From ac1b398b4db6d1bdc60d6da8e809487254d17a87 Mon Sep 17 00:00:00 2001
From: Erik <erikdesjardins@users.noreply.github.com>
Date: Fri, 13 Jul 2018 15:31:57 -0400
Subject: [PATCH 01/16] seal extension traits to prevent external
 implementation

---
 library/compiler-builtins/libm/src/lib.rs | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/library/compiler-builtins/libm/src/lib.rs b/library/compiler-builtins/libm/src/lib.rs
index fa709ad754a9..4deb2e21eee5 100644
--- a/library/compiler-builtins/libm/src/lib.rs
+++ b/library/compiler-builtins/libm/src/lib.rs
@@ -32,9 +32,8 @@ pub fn _eq(a: u64, b: u64) -> bool {
 
 /// Math support for `f32`
 ///
-/// NOTE this meant to be a closed extension trait. The only stable way to use this trait is to
-/// import it to access its methods.
-pub trait F32Ext {
+/// This trait is sealed and cannot be implemented outside of `libm`.
+pub trait F32Ext: private::Sealed {
     #[cfg(todo)]
     fn floor(self) -> Self;
 
@@ -360,9 +359,8 @@ impl F32Ext for f32 {
 
 /// Math support for `f32`
 ///
-/// NOTE this meant to be a closed extension trait. The only stable way to use this trait is to
-/// import it to access its methods.
-pub trait F64Ext {
+/// This trait is sealed and cannot be implemented outside of `libm`.
+pub trait F64Ext: private::Sealed {
     fn floor(self) -> Self;
 
     #[cfg(todo)]
@@ -691,3 +689,10 @@ impl F64Ext for f64 {
         0.5 * ((2.0 * self) / (1.0 - self)).ln_1p()
     }
 }
+
+mod private {
+    pub trait Sealed {}
+
+    impl Sealed for f32 {}
+    impl Sealed for f64 {}
+}

From 1ba1301250f58ada230ff0211c383e59eb884f6a Mon Sep 17 00:00:00 2001
From: Jorge Aparicio <jorge@japaric.io>
Date: Fri, 13 Jul 2018 16:32:57 -0500
Subject: [PATCH 02/16] catch panics in tests

so we can print the inputs that triggered the panic
---
 .../libm/test-generator/src/main.rs           | 207 +++++++++++++-----
 1 file changed, 149 insertions(+), 58 deletions(-)

diff --git a/library/compiler-builtins/libm/test-generator/src/main.rs b/library/compiler-builtins/libm/test-generator/src/main.rs
index 6353b257dce3..ca49179f187e 100644
--- a/library/compiler-builtins/libm/test-generator/src/main.rs
+++ b/library/compiler-builtins/libm/test-generator/src/main.rs
@@ -62,6 +62,8 @@ macro_rules! f32_f32 {
 
                     extern crate libm;
 
+                    use std::panic;
+
                     #[test]
                     fn {0}() {{
                         const CASES: &[(u32, u32)] = &[
@@ -71,16 +73,23 @@ macro_rules! f32_f32 {
                         for case in CASES {{
                             let (inp, expected) = *case;
 
-                            let outf = libm::{0}(f32::from_bits(inp));
-                            let outi = outf.to_bits();
+                            if let Ok(outf) =
+                                panic::catch_unwind(|| libm::{0}(f32::from_bits(inp)))
+                            {{
+                                let outi = outf.to_bits();
 
-                            if !((outf.is_nan() && f32::from_bits(expected).is_nan()) ||
-                                 libm::_eqf(outi, expected)) {{
+                                if !((outf.is_nan() && f32::from_bits(expected).is_nan())
+                                    || libm::_eqf(outi, expected))
+                                {{
+                                    panic!(
+                                        \"input: {{}}, output: {{}}, expected: {{}}\",
+                                        inp, outi, expected,
+                                    );
+                                }}
+                            }} else {{
                                 panic!(
-                                    \"input: {{}}, output: {{}}, expected: {{}}\",
-                                    inp,
-                                    outi,
-                                    expected,
+                                    \"input: {{}}, output: PANIC, expected: {{}}\",
+                                    inp, expected,
                                 );
                             }}
                         }}
@@ -124,6 +133,8 @@ macro_rules! f32f32_f32 {
 
                     extern crate libm;
 
+                    use std::panic;
+
                     #[test]
                     fn {0}() {{
                         const CASES: &[((u32, u32), u32)] = &[
@@ -133,15 +144,25 @@ macro_rules! f32f32_f32 {
                         for case in CASES {{
                             let ((i1, i2), expected) = *case;
 
-                            let outf = libm::{0}(f32::from_bits(i1), f32::from_bits(i2));
-                            let outi = outf.to_bits();
+                            if let Ok(outf) = panic::catch_unwind(|| {{
+                                libm::{0}(f32::from_bits(i1), f32::from_bits(i2))
+                            }}) {{
+                                let outi = outf.to_bits();
 
-                            if !((outf.is_nan() && f32::from_bits(expected).is_nan()) ||
-                                 libm::_eqf(outi, expected)) {{
+                                if !((outf.is_nan() && f32::from_bits(expected).is_nan())
+                                    || libm::_eqf(outi, expected))
+                                {{
+                                    panic!(
+                                        \"input: {{:?}}, output: {{}}, expected: {{}}\",
+                                        (i1, i2),
+                                        outi,
+                                        expected,
+                                    );
+                                }}
+                            }} else {{
                                 panic!(
-                                    \"input: {{:?}}, output: {{}}, expected: {{}}\",
+                                    \"input: {{:?}}, output: PANIC, expected: {{}}\",
                                     (i1, i2),
-                                    outi,
                                     expected,
                                 );
                             }}
@@ -188,6 +209,8 @@ macro_rules! f32f32f32_f32 {
 
                     extern crate libm;
 
+                    use std::panic;
+
                     #[test]
                     fn {0}() {{
                         const CASES: &[((u32, u32, u32), u32)] = &[
@@ -197,19 +220,29 @@ macro_rules! f32f32f32_f32 {
                         for case in CASES {{
                             let ((i1, i2, i3), expected) = *case;
 
-                            let outf = libm::{0}(
-                                f32::from_bits(i1),
-                                f32::from_bits(i2),
-                                f32::from_bits(i3),
-                            );
-                            let outi = outf.to_bits();
+                            if let Ok(outf) = panic::catch_unwind(|| {{
+                                libm::{0}(
+                                    f32::from_bits(i1),
+                                    f32::from_bits(i2),
+                                    f32::from_bits(i3),
+                                )
+                            }}) {{
+                                let outi = outf.to_bits();
 
-                            if !((outf.is_nan() && f32::from_bits(expected).is_nan()) ||
-                                 libm::_eqf(outi, expected)) {{
+                                if !((outf.is_nan() && f32::from_bits(expected).is_nan())
+                                    || libm::_eqf(outi, expected))
+                                {{
+                                    panic!(
+                                        \"input: {{:?}}, output: {{}}, expected: {{}}\",
+                                        (i1, i2, i3),
+                                        outi,
+                                        expected,
+                                    );
+                                }}
+                            }} else {{
                                 panic!(
-                                    \"input: {{:?}}, output: {{}}, expected: {{}}\",
+                                    \"input: {{:?}}, output: PANIC, expected: {{}}\",
                                     (i1, i2, i3),
-                                    outi,
                                     expected,
                                 );
                             }}
@@ -253,6 +286,8 @@ macro_rules! f32i32_f32 {
 
                     extern crate libm;
 
+                    use std::panic;
+
                     #[test]
                     fn {0}() {{
                         const CASES: &[((u32, i16), u32)] = &[
@@ -262,15 +297,25 @@ macro_rules! f32i32_f32 {
                         for case in CASES {{
                             let ((i1, i2), expected) = *case;
 
-                            let outf = libm::{0}(f32::from_bits(i1), i2 as i32);
-                            let outi = outf.to_bits();
+                            if let Ok(outf) = panic::catch_unwind(|| {{
+                                libm::{0}(f32::from_bits(i1), i2 as i32)
+                            }}) {{
+                                let outi = outf.to_bits();
 
-                            if !((outf.is_nan() && f32::from_bits(expected).is_nan()) ||
-                                 libm::_eqf(outi, expected)) {{
+                                if !((outf.is_nan() && f32::from_bits(expected).is_nan())
+                                    || libm::_eqf(outi, expected))
+                                {{
+                                    panic!(
+                                        \"input: {{:?}}, output: {{}}, expected: {{}}\",
+                                        (i1, i2),
+                                        outi,
+                                        expected,
+                                    );
+                                }}
+                            }} else {{
                                 panic!(
-                                    \"input: {{:?}}, output: {{}}, expected: {{}}\",
+                                    \"input: {{:?}}, output: PANIC, expected: {{}}\",
                                     (i1, i2),
-                                    outi,
                                     expected,
                                 );
                             }}
@@ -314,6 +359,8 @@ macro_rules! f64_f64 {
 
                     extern crate libm;
 
+                    use std::panic;
+
                     #[test]
                     fn {0}() {{
                         const CASES: &[(u64, u64)] = &[
@@ -323,15 +370,25 @@ macro_rules! f64_f64 {
                         for case in CASES {{
                             let (inp, expected) = *case;
 
-                            let outf = libm::{0}(f64::from_bits(inp));
-                            let outi = outf.to_bits();
+                            if let Ok(outf) = panic::catch_unwind(|| {{
+                                libm::{0}(f64::from_bits(inp))
+                            }}) {{
+                                let outi = outf.to_bits();
 
-                            if !((outf.is_nan() && f64::from_bits(expected).is_nan()) ||
-                                 libm::_eq(outi, expected)) {{
+                                if !((outf.is_nan() && f64::from_bits(expected).is_nan())
+                                    || libm::_eq(outi, expected))
+                                {{
+                                    panic!(
+                                        \"input: {{}}, output: {{}}, expected: {{}}\",
+                                        inp,
+                                        outi,
+                                        expected,
+                                    );
+                                }}
+                            }} else {{
                                 panic!(
-                                    \"input: {{}}, output: {{}}, expected: {{}}\",
+                                    \"input: {{}}, output: PANIC, expected: {{}}\",
                                     inp,
-                                    outi,
                                     expected,
                                 );
                             }}
@@ -376,6 +433,8 @@ macro_rules! f64f64_f64 {
 
                     extern crate libm;
 
+                    use std::panic;
+
                     #[test]
                     fn {0}() {{
                         const CASES: &[((u64, u64), u64)] = &[
@@ -385,15 +444,24 @@ macro_rules! f64f64_f64 {
                         for case in CASES {{
                             let ((i1, i2), expected) = *case;
 
-                            let outf = libm::{0}(f64::from_bits(i1), f64::from_bits(i2));
-                            let outi = outf.to_bits();
+                            if let Ok(outf) = panic::catch_unwind(|| {{
+                                libm::{0}(f64::from_bits(i1), f64::from_bits(i2))
+                            }}) {{
+                                let outi = outf.to_bits();
 
-                            if !((outf.is_nan() && f64::from_bits(expected).is_nan()) ||
-                                 libm::_eq(outi, expected)) {{
+                                if !((outf.is_nan() && f64::from_bits(expected).is_nan()) ||
+                                    libm::_eq(outi, expected)) {{
+                                    panic!(
+                                        \"input: {{:?}}, output: {{}}, expected: {{}}\",
+                                        (i1, i2),
+                                        outi,
+                                        expected,
+                                    );
+                                }}
+                            }} else {{
                                 panic!(
-                                    \"input: {{:?}}, output: {{}}, expected: {{}}\",
+                                    \"input: {{:?}}, output: PANIC, expected: {{}}\",
                                     (i1, i2),
-                                    outi,
                                     expected,
                                 );
                             }}
@@ -440,6 +508,8 @@ macro_rules! f64f64f64_f64 {
 
                     extern crate libm;
 
+                    use std::panic;
+
                     #[test]
                     fn {0}() {{
                         const CASES: &[((u64, u64, u64), u64)] = &[
@@ -449,19 +519,29 @@ macro_rules! f64f64f64_f64 {
                         for case in CASES {{
                             let ((i1, i2, i3), expected) = *case;
 
-                            let outf = libm::{0}(
-                                f64::from_bits(i1),
-                                f64::from_bits(i2),
-                                f64::from_bits(i3),
-                            );
-                            let outi = outf.to_bits();
+                            if let Ok(outf) = panic::catch_unwind(|| {{
+                                libm::{0}(
+                                    f64::from_bits(i1),
+                                    f64::from_bits(i2),
+                                    f64::from_bits(i3),
+                                )
+                            }}) {{
+                                let outi = outf.to_bits();
 
-                            if !((outf.is_nan() && f64::from_bits(expected).is_nan()) ||
-                                 libm::_eq(outi, expected)) {{
+                                if !((outf.is_nan() && f64::from_bits(expected).is_nan())
+                                    || libm::_eq(outi, expected))
+                                {{
+                                    panic!(
+                                        \"input: {{:?}}, output: {{}}, expected: {{}}\",
+                                        (i1, i2, i3),
+                                        outi,
+                                        expected,
+                                    );
+                                }}
+                            }} else {{
                                 panic!(
-                                    \"input: {{:?}}, output: {{}}, expected: {{}}\",
+                                    \"input: {{:?}}, output: PANIC, expected: {{}}\",
                                     (i1, i2, i3),
-                                    outi,
                                     expected,
                                 );
                             }}
@@ -505,6 +585,8 @@ macro_rules! f64i32_f64 {
 
                     extern crate libm;
 
+                    use std::panic;
+
                     #[test]
                     fn {0}() {{
                         const CASES: &[((u64, i16), u64)] = &[
@@ -514,15 +596,24 @@ macro_rules! f64i32_f64 {
                         for case in CASES {{
                             let ((i1, i2), expected) = *case;
 
-                            let outf = libm::{0}(f64::from_bits(i1), i2 as i32);
-                            let outi = outf.to_bits();
+                            if let Ok(outf) = panic::catch_unwind(|| {{
+                                libm::{0}(f64::from_bits(i1), i2 as i32)
+                            }}) {{
+                                let outi = outf.to_bits();
 
-                            if !((outf.is_nan() && f64::from_bits(expected).is_nan()) ||
-                                 libm::_eq(outi, expected)) {{
+                                if !((outf.is_nan() && f64::from_bits(expected).is_nan()) ||
+                                    libm::_eq(outi, expected)) {{
+                                    panic!(
+                                        \"input: {{:?}}, output: {{}}, expected: {{}}\",
+                                        (i1, i2),
+                                        outi,
+                                        expected,
+                                    );
+                                }}
+                            }} else {{
                                 panic!(
-                                    \"input: {{:?}}, output: {{}}, expected: {{}}\",
+                                    \"input: {{:?}}, output: PANIC, expected: {{}}\",
                                     (i1, i2),
-                                    outi,
                                     expected,
                                 );
                             }}

From 6dbd8b33035d2f40eb7f4def4f340081d4234ed5 Mon Sep 17 00:00:00 2001
From: Erik <erikdesjardins@users.noreply.github.com>
Date: Fri, 13 Jul 2018 17:41:54 -0400
Subject: [PATCH 03/16] implement hypotf

---
 library/compiler-builtins/libm/src/lib.rs     |  2 -
 .../compiler-builtins/libm/src/math/hypotf.rs | 43 +++++++++++++++++++
 .../compiler-builtins/libm/src/math/mod.rs    |  2 +
 .../libm/test-generator/src/main.rs           |  2 +-
 4 files changed, 46 insertions(+), 3 deletions(-)
 create mode 100644 library/compiler-builtins/libm/src/math/hypotf.rs

diff --git a/library/compiler-builtins/libm/src/lib.rs b/library/compiler-builtins/libm/src/lib.rs
index fa709ad754a9..a6702c4a72b7 100644
--- a/library/compiler-builtins/libm/src/lib.rs
+++ b/library/compiler-builtins/libm/src/lib.rs
@@ -88,7 +88,6 @@ pub trait F32Ext {
     #[cfg(todo)]
     fn cbrt(self) -> Self;
 
-    #[cfg(todo)]
     fn hypot(self, other: Self) -> Self;
 
     #[cfg(todo)]
@@ -254,7 +253,6 @@ impl F32Ext for f32 {
         cbrtf(self)
     }
 
-    #[cfg(todo)]
     #[inline]
     fn hypot(self, other: Self) -> Self {
         hypotf(self, other)
diff --git a/library/compiler-builtins/libm/src/math/hypotf.rs b/library/compiler-builtins/libm/src/math/hypotf.rs
new file mode 100644
index 000000000000..146aab4e4464
--- /dev/null
+++ b/library/compiler-builtins/libm/src/math/hypotf.rs
@@ -0,0 +1,43 @@
+use core::f32;
+
+use super::sqrtf;
+
+#[inline]
+pub fn hypotf(mut x: f32, mut y: f32) -> f32 {
+    let x1p90 = f32::from_bits(0x6c800000); // 0x1p90f === 2 ^ 90
+    let x1p_90 = f32::from_bits(0x12800000); // 0x1p-90f === 2 ^ -90
+
+    let mut uxi = x.to_bits();
+    let mut uyi = y.to_bits();
+    let uti;
+    let mut z: f32;
+
+    uxi &= -1i32 as u32 >> 1;
+    uyi &= -1i32 as u32 >> 1;
+    if uxi < uyi {
+        uti = uxi;
+        uxi = uyi;
+        uyi = uti;
+    }
+
+    x = f32::from_bits(uxi);
+    y = f32::from_bits(uyi);
+    if uyi == 0xff<<23 {
+        return y;
+    }
+    if uxi >= 0xff<<23 || uyi == 0 || uxi - uyi >= 25<<23 {
+        return x + y;
+    }
+
+    z = 1.;
+    if uxi >= (0x7f+60)<<23 {
+        z = x1p90;
+        x *= x1p_90;
+        y *= x1p_90;
+    } else if uyi < (0x7f-60)<<23 {
+        z = x1p_90;
+        x *= x1p90;
+        y *= x1p90;
+    }
+    z*sqrtf((x as f64 * x as f64 + y as f64 * y as f64) as f32)
+}
diff --git a/library/compiler-builtins/libm/src/math/mod.rs b/library/compiler-builtins/libm/src/math/mod.rs
index 71b58dda8832..a34ebd767e54 100644
--- a/library/compiler-builtins/libm/src/math/mod.rs
+++ b/library/compiler-builtins/libm/src/math/mod.rs
@@ -17,6 +17,7 @@ mod expf;
 mod floor;
 mod trunc;
 mod truncf;
+mod hypotf;
 
 //mod service;
 
@@ -34,6 +35,7 @@ pub use self::{
     floor::floor,
     trunc::trunc,
     truncf::truncf,
+    hypotf::hypotf,
 };
 
 fn isnanf(x: f32) -> bool {
diff --git a/library/compiler-builtins/libm/test-generator/src/main.rs b/library/compiler-builtins/libm/test-generator/src/main.rs
index 6353b257dce3..290952bbd187 100644
--- a/library/compiler-builtins/libm/test-generator/src/main.rs
+++ b/library/compiler-builtins/libm/test-generator/src/main.rs
@@ -587,7 +587,7 @@ f32_f32! {
 // With signature `fn(f32, f32) -> f32`
 f32f32_f32! {
     // atan2f,
-    // hypotf,
+    hypotf,
     fmodf,
     powf,
 }

From 892cd4f5b83761f2abf96e27c109ad3a6d87bceb Mon Sep 17 00:00:00 2001
From: Erik <erikdesjardins@users.noreply.github.com>
Date: Fri, 13 Jul 2018 18:31:01 -0400
Subject: [PATCH 04/16] implement sqrt and hypot

---
 library/compiler-builtins/libm/src/lib.rs     |   4 -
 .../compiler-builtins/libm/src/math/hypot.rs  |  74 ++++++++++
 .../compiler-builtins/libm/src/math/mod.rs    |   4 +
 .../compiler-builtins/libm/src/math/sqrt.rs   | 129 ++++++++++++++++++
 .../libm/test-generator/src/main.rs           |   4 +-
 5 files changed, 209 insertions(+), 6 deletions(-)
 create mode 100644 library/compiler-builtins/libm/src/math/hypot.rs
 create mode 100644 library/compiler-builtins/libm/src/math/sqrt.rs

diff --git a/library/compiler-builtins/libm/src/lib.rs b/library/compiler-builtins/libm/src/lib.rs
index 0fb555a7b499..3e25c16db29d 100644
--- a/library/compiler-builtins/libm/src/lib.rs
+++ b/library/compiler-builtins/libm/src/lib.rs
@@ -391,7 +391,6 @@ pub trait F64Ext: private::Sealed {
     #[cfg(todo)]
     fn powf(self, n: Self) -> Self;
 
-    #[cfg(todo)]
     fn sqrt(self) -> Self;
 
     #[cfg(todo)]
@@ -415,7 +414,6 @@ pub trait F64Ext: private::Sealed {
     #[cfg(todo)]
     fn cbrt(self) -> Self;
 
-    #[cfg(todo)]
     fn hypot(self, other: Self) -> Self;
 
     #[cfg(todo)]
@@ -536,7 +534,6 @@ impl F64Ext for f64 {
         pow(self, n)
     }
 
-    #[cfg(todo)]
     #[inline]
     fn sqrt(self) -> Self {
         sqrt(self)
@@ -584,7 +581,6 @@ impl F64Ext for f64 {
         cbrt(self)
     }
 
-    #[cfg(todo)]
     #[inline]
     fn hypot(self, other: Self) -> Self {
         hypot(self, other)
diff --git a/library/compiler-builtins/libm/src/math/hypot.rs b/library/compiler-builtins/libm/src/math/hypot.rs
new file mode 100644
index 000000000000..dcc17d914fb9
--- /dev/null
+++ b/library/compiler-builtins/libm/src/math/hypot.rs
@@ -0,0 +1,74 @@
+use core::f64;
+
+use super::sqrt;
+
+const SPLIT: f64 = 134217728. + 1.; // 0x1p27 + 1 === (2 ^ 27) + 1
+
+fn sq(x: f64) -> (f64, f64) {
+    let xh: f64;
+    let xl: f64;
+    let xc: f64;
+
+    xc = x * SPLIT;
+    xh = x - xc + xc;
+    xl = x - xh;
+    let hi = x*x;
+    let lo = xh*xh - hi + 2.*xh*xl + xl*xl;
+    (hi, lo)
+}
+
+#[inline]
+pub fn hypot(mut x: f64, mut y: f64) -> f64 {
+    let x1p700 = f64::from_bits(0x6bb0000000000000); // 0x1p700 === 2 ^ 700
+    let x1p_700 = f64::from_bits(0x1430000000000000); // 0x1p-700 === 2 ^ -700
+
+    let mut uxi = x.to_bits();
+    let mut uyi = y.to_bits();
+    let uti;
+    let ex: i64;
+    let ey: i64;
+    let mut z: f64;
+
+    /* arrange |x| >= |y| */
+    uxi &= -1i64 as u64 >> 1;
+    uyi &= -1i64 as u64 >> 1;
+    if uxi < uyi {
+        uti = uxi;
+        uxi = uyi;
+        uyi = uti;
+    }
+
+    /* special cases */
+    ex = (uxi>>52) as i64;
+    ey = (uyi>>52) as i64;
+    x = f64::from_bits(uxi);
+    y = f64::from_bits(uyi);
+    /* note: hypot(inf,nan) == inf */
+    if ey == 0x7ff {
+        return y;
+    }
+    if ex == 0x7ff || uyi == 0 {
+        return x;
+    }
+    /* note: hypot(x,y) ~= x + y*y/x/2 with inexact for small y/x */
+    /* 64 difference is enough for ld80 double_t */
+    if ex - ey > 64 {
+        return x + y;
+    }
+
+    /* precise sqrt argument in nearest rounding mode without overflow */
+    /* xh*xh must not overflow and xl*xl must not underflow in sq */
+    z = 1.;
+    if ex > 0x3ff+510 {
+        z = x1p700;
+        x *= x1p_700;
+        y *= x1p_700;
+    } else if ey < 0x3ff-450 {
+        z = x1p_700;
+        x *= x1p700;
+        y *= x1p700;
+    }
+    let (hx, lx) = sq(x);
+    let (hy, ly) = sq(y);
+    return z*sqrt(ly+lx+hy+hx);
+}
diff --git a/library/compiler-builtins/libm/src/math/mod.rs b/library/compiler-builtins/libm/src/math/mod.rs
index a34ebd767e54..444652e81eff 100644
--- a/library/compiler-builtins/libm/src/math/mod.rs
+++ b/library/compiler-builtins/libm/src/math/mod.rs
@@ -11,12 +11,14 @@ mod powf;
 mod round;
 mod scalbn;
 mod scalbnf;
+mod sqrt;
 mod sqrtf;
 mod logf;
 mod expf;
 mod floor;
 mod trunc;
 mod truncf;
+mod hypot;
 mod hypotf;
 
 //mod service;
@@ -29,12 +31,14 @@ pub use self::{
     round::round,
     scalbn::scalbn,
     scalbnf::scalbnf,
+    sqrt::sqrt,
     sqrtf::sqrtf,
     logf::logf,
     expf::expf,
     floor::floor,
     trunc::trunc,
     truncf::truncf,
+    hypot::hypot,
     hypotf::hypotf,
 };
 
diff --git a/library/compiler-builtins/libm/src/math/sqrt.rs b/library/compiler-builtins/libm/src/math/sqrt.rs
new file mode 100644
index 000000000000..49fc58fff03c
--- /dev/null
+++ b/library/compiler-builtins/libm/src/math/sqrt.rs
@@ -0,0 +1,129 @@
+use core::f64;
+
+const TINY: f64 = 1.0e-300;
+
+#[inline]
+pub fn sqrt(x: f64) -> f64 {
+    let mut z: f64;
+    let sign: u32 = 0x80000000;
+    let mut ix0: i32;
+    let mut s0: i32;
+    let mut q: i32;
+    let mut m: i32;
+    let mut t: i32;
+    let mut i: i32;
+    let mut r: u32;
+    let mut t1: u32;
+    let mut s1: u32;
+    let mut ix1: u32;
+    let mut q1: u32;
+
+    ix0 = (x.to_bits() >> 32) as i32;
+    ix1 = x.to_bits() as u32;
+
+    /* take care of Inf and NaN */
+    if (ix0&0x7ff00000) == 0x7ff00000 {
+        return x*x + x;  /* sqrt(NaN)=NaN, sqrt(+inf)=+inf, sqrt(-inf)=sNaN */
+    }
+    /* take care of zero */
+    if ix0 <= 0 {
+        if ((ix0&!(sign as i32))|ix1 as i32) == 0 {
+            return x;  /* sqrt(+-0) = +-0 */
+        }
+        if ix0 < 0 {
+            return (x - x) / (x - x);  /* sqrt(-ve) = sNaN */
+        }
+    }
+    /* normalize x */
+    m = ix0>>20;
+    if m == 0 {  /* subnormal x */
+        while ix0 == 0 {
+            m -= 21;
+            ix0 |= (ix1>>11) as i32;
+            ix1 <<= 21;
+        }
+        i=0;
+        while (ix0&0x00100000) == 0 {
+            i += 1;
+            ix0 <<= 1;
+        }
+        m -= i - 1;
+        ix0 |= (ix1>>(32-i)) as i32;
+        ix1 <<= i;
+    }
+    m -= 1023;    /* unbias exponent */
+    ix0 = (ix0&0x000fffff)|0x00100000;
+    if (m & 1) == 1 {  /* odd m, double x to make it even */
+        ix0 += ix0 + ((ix1&sign)>>31) as i32;
+        ix1 += ix1;
+    }
+    m >>= 1;      /* m = [m/2] */
+
+    /* generate sqrt(x) bit by bit */
+    ix0 += ix0 + ((ix1&sign)>>31) as i32;
+    ix1 += ix1;
+    q = 0; /* [q,q1] = sqrt(x) */
+    q1 = 0;
+    s0 = 0;
+    s1 = 0;
+    r = 0x00200000;        /* r = moving bit from right to left */
+
+    while r != 0 {
+        t = s0 + r as i32;
+        if t <= ix0 {
+            s0   = t + r as i32;
+            ix0 -= t;
+            q   += r as i32;
+        }
+        ix0 += ix0 + ((ix1&sign)>>31) as i32;
+        ix1 += ix1;
+        r >>= 1;
+    }
+
+    r = sign;
+    while r != 0 {
+        t1 = s1 + r;
+        t  = s0;
+        if t < ix0 || (t == ix0 && t1 <= ix1) {
+            s1 = t1 + r;
+            if (t1&sign) == sign && (s1&sign) == 0 {
+                s0 += 1;
+            }
+            ix0 -= t;
+            if ix1 < t1 {
+                ix0 -= 1;
+            }
+            ix1 -= t1;
+            q1 += r;
+        }
+        ix0 += ix0 + ((ix1&sign)>>31) as i32;
+        ix1 += ix1;
+        r >>= 1;
+    }
+
+    /* use floating add to find out rounding direction */
+    if (ix0 as u32|ix1) != 0 {
+        z = 1.0 - TINY; /* raise inexact flag */
+        if z >= 1.0 {
+            z = 1.0 + TINY;
+            if q1 == 0xffffffff {
+                q1 = 0;
+                q+=1;
+            } else if z > 1.0 {
+                if q1 == 0xfffffffe {
+                    q += 1;
+                }
+                q1 += 2;
+            } else {
+                q1 += q1 & 1;
+            }
+        }
+    }
+    ix0 = (q>>1) + 0x3fe00000;
+    ix1 = q1>>1;
+    if (q&1) == 1 {
+        ix1 |= sign;
+    }
+    ix0 += m << 20;
+    f64::from_bits((ix0 as u64) << 32 | ix1 as u64)
+}
diff --git a/library/compiler-builtins/libm/test-generator/src/main.rs b/library/compiler-builtins/libm/test-generator/src/main.rs
index 8da1a920eef2..ce20e80d1952 100644
--- a/library/compiler-builtins/libm/test-generator/src/main.rs
+++ b/library/compiler-builtins/libm/test-generator/src/main.rs
@@ -713,7 +713,7 @@ f64_f64! {
     round,
     // sin,
     // sinh,
-    // sqrt,
+    sqrt,
     // tan,
     // tanh,
     trunc,
@@ -725,7 +725,7 @@ f64f64_f64! {
     // atan2,
     // fdim,
     // fmod,
-    // hypot,
+    hypot,
     // pow,
 }
 

From aaa56fba356a4961baf98ccb8d8ff85c589ea19c Mon Sep 17 00:00:00 2001
From: Jorge Aparicio <jorge@japaric.io>
Date: Fri, 13 Jul 2018 17:52:58 -0500
Subject: [PATCH 05/16] move a chunk of the README into CONTRIBUTING.md

---
 .../compiler-builtins/libm/CONTRIBUTING.md    | 87 +++++++++++++++++++
 library/compiler-builtins/libm/README.md      | 52 +----------
 library/compiler-builtins/libm/src/lib.rs     |  2 +-
 .../compiler-builtins/libm/src/math/trunc.rs  |  8 ++
 .../compiler-builtins/libm/src/math/truncf.rs |  8 ++
 5 files changed, 105 insertions(+), 52 deletions(-)
 create mode 100644 library/compiler-builtins/libm/CONTRIBUTING.md

diff --git a/library/compiler-builtins/libm/CONTRIBUTING.md b/library/compiler-builtins/libm/CONTRIBUTING.md
new file mode 100644
index 000000000000..1f0a05a3f8d9
--- /dev/null
+++ b/library/compiler-builtins/libm/CONTRIBUTING.md
@@ -0,0 +1,87 @@
+# How to contribute
+
+- Pick your favorite math function from the [issue tracker].
+- Look for the C implementation of the function in the [MUSL source code][src].
+- Copy paste the C code into a Rust file in the `src/math` directory and adjust `src/math/mod.rs`
+  accordingly. Also, uncomment the corresponding trait method in `src/lib.rs`.
+- Run `cargo watch check` and fix the compiler errors.
+- Tweak the bottom of `test-generator/src/main.rs` to add your function to the test suite.
+- If you can, run the full test suite locally (see the [testing](#testing) section below). If you
+  can't, no problem! Your PR will be fully tested automatically. Though you may still want to add
+  and run some unit tests. See the bottom of [`src/math/truncf.rs`] for an example of such tests;
+  you can run unit tests with the `cargo test --lib` command.
+- Send us a pull request!
+- :tada:
+
+[issue tracker]: https://github.com/japaric/libm/issues
+[src]: https://git.musl-libc.org/cgit/musl/tree/src/math
+[`src/math/truncf.rs`]: https://github.com/japaric/libm/blob/master/src/math/truncf.rs
+
+Check [PR #65] for an example.
+
+[PR #65]: https://github.com/japaric/libm/pull/65
+
+## Tips and tricks
+
+- *IMPORTANT* The code in this crate will end up being used in the `core` crate so it can **not**
+  have any external dependencies (other than `core` itself).
+
+- Only use relative imports within the `math` directory / module, e.g. `use self::fabs::fabs` or
+`use super::isnanf`. Absolute imports from core are OK, e.g. `use core::u64`.
+
+- To reinterpret a float as an integer use the `to_bits` method. The MUSL code uses the
+  `GET_FLOAT_WORD` macro, or a union, to do this operation.
+
+- To reinterpret an integer as a float use the `f32::from_bits` constructor. The MUSL code uses the
+  `SET_FLOAT_WORD` macro, or a union, to do this operation.
+
+- You may encounter weird literals like `0x1p127f` in the MUSL code. These are hexadecimal floating
+  point literals. Rust (the language) doesn't support these kind of literals. The best way I have
+  found to deal with these literals is to turn them into their integer representation using the
+  [`hexf!`] macro and then turn them back into floats. See below:
+
+[`hexf!`]: https://crates.io/crates/hexf
+
+``` rust
+// Step 1: write a program to convert the float into its integer representation
+#[macro_use]
+extern crate hexf;
+
+fn main() {
+    println!("{:#x}", hexf32!("0x1.0p127").to_bits());
+}
+```
+
+``` console
+$ # Step 2: run the program
+$ cargo run
+0x7f000000
+```
+
+``` rust
+// Step 3: copy paste the output into libm
+let x1p127 = f32::from_bits(0x7f000000); // 0x1p127f === 2 ^ 12
+```
+
+- Rust code panics on arithmetic overflows when not optimized. You may need to use the [`Wrapping`]
+  newtype to avoid this problem.
+
+[`Wrapping`]: https://doc.rust-lang.org/std/num/struct.Wrapping.html
+
+## Testing
+
+The test suite of this crate can only be run on x86_64 Linux systems using the following commands:
+
+``` console
+$ # The test suite depends on the `cross` tool so install it if you don't have it
+$ cargo install cross
+
+$ # and the `cross` tool requires docker to be running
+$ systemctl start docker
+
+$ # execute the test suite for the x86_64 target
+$ TARGET=x86_64-unknown-linux-gnu bash ci/script.sh
+
+$ # execute the test suite for the ARMv7 target
+$ TARGET=armv7-unknown-linux-gnueabihf bash ci/script.sh
+```
diff --git a/library/compiler-builtins/libm/README.md b/library/compiler-builtins/libm/README.md
index cb29baf63a7b..ce731a203d60 100644
--- a/library/compiler-builtins/libm/README.md
+++ b/library/compiler-builtins/libm/README.md
@@ -9,59 +9,9 @@ A port of [MUSL]'s libm to Rust.
 The short term goal of this library is to enable math support (e.g. `sin`, `atan2`) for the
 `wasm32-unknown-unknown` target. The longer term goal is to enable math support in the `core` crate.
 
-## Testing
-
-The test suite of this crate can only be run on x86_64 Linux systems.
-
-```
-$ # The test suite depends on the `cross` tool so install it if you don't have it
-$ cargo install cross
-
-$ # and the `cross` tool requires docker to be running
-$ systemctl start docker
-
-$ # execute the test suite for the x86_64 target
-$ TARGET=x86_64-unknown-linux-gnu bash ci/script.sh
-
-$ # execute the test suite for the ARMv7 target
-$ TARGET=armv7-unknown-linux-gnueabihf bash ci/script.sh
-```
-
 ## Contributing
 
-- Pick your favorite math function from the [issue tracker].
-- Look for the C implementation of the function in the [MUSL source code][src].
-- Copy paste the C code into a Rust file in the `src/math` directory and adjust `src/math/mod.rs`
-  accordingly. Also, uncomment the corresponding trait method in `src/lib.rs`.
-- Run `cargo watch check` and fix the compiler errors.
-- Tweak the bottom of `test-generator/src/main.rs` to add your function to the test suite.
-- If you can, run the test suite locally. If you can't, no problem! Your PR will be tested
-  automatically.
-- Send us a pull request!
-- :tada:
-
-[issue tracker]: https://github.com/japaric/libm/issues
-[src]: https://git.musl-libc.org/cgit/musl/tree/src/math
-
-Check [PR #2] for an example.
-
-[PR #2]: https://github.com/japaric/libm/pull/2
-
-### Notes
-
-- Only use relative imports within the `math` directory / module, e.g. `use self::fabs::fabs` or
-`use super::isnanf`. Absolute imports from core are OK, e.g. `use core::u64`.
-
-- To reinterpret a float as an integer use the `to_bits` method. The MUSL code uses the
-  `GET_FLOAT_WORD` macro, or a union, to do this operation.
-
-- To reinterpret an integer as a float use the `f32::from_bits` constructor. The MUSL code uses the
-  `SET_FLOAT_WORD` macro, or a union, to do this operation.
-
-- Rust code panics on arithmetic overflows when not optimized. You may need to use the [`Wrapping`]
-  newtype to avoid this problem.
-
-[`Wrapping`]: https://doc.rust-lang.org/std/num/struct.Wrapping.html
+Please check [CONTRIBUTING.md](CONTRIBUTING.md)
 
 ## License
 
diff --git a/library/compiler-builtins/libm/src/lib.rs b/library/compiler-builtins/libm/src/lib.rs
index 0fb555a7b499..32735f7ed6ba 100644
--- a/library/compiler-builtins/libm/src/lib.rs
+++ b/library/compiler-builtins/libm/src/lib.rs
@@ -355,7 +355,7 @@ impl F32Ext for f32 {
     }
 }
 
-/// Math support for `f32`
+/// Math support for `f64`
 ///
 /// This trait is sealed and cannot be implemented outside of `libm`.
 pub trait F64Ext: private::Sealed {
diff --git a/library/compiler-builtins/libm/src/math/trunc.rs b/library/compiler-builtins/libm/src/math/trunc.rs
index b50ffd77156a..6bea67cbc165 100644
--- a/library/compiler-builtins/libm/src/math/trunc.rs
+++ b/library/compiler-builtins/libm/src/math/trunc.rs
@@ -22,3 +22,11 @@ pub fn trunc(x: f64) -> f64 {
     i &= !m;
     f64::from_bits(i)
 }
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn sanity_check() {
+        assert_eq!(super::trunc(1.1), 1.0);
+    }
+}
diff --git a/library/compiler-builtins/libm/src/math/truncf.rs b/library/compiler-builtins/libm/src/math/truncf.rs
index f7d7249e3519..9d42620d9666 100644
--- a/library/compiler-builtins/libm/src/math/truncf.rs
+++ b/library/compiler-builtins/libm/src/math/truncf.rs
@@ -22,3 +22,11 @@ pub fn truncf(x: f32) -> f32 {
     i &= !m;
     f32::from_bits(i)
 }
+
+#[cfg(test)]
+mod tests {
+    #[test]
+    fn sanity_check() {
+        assert_eq!(super::truncf(1.1), 1.0);
+    }
+}

From e6576930ef34b5617c0c46faa0937922fed9095d Mon Sep 17 00:00:00 2001
From: Jorge Aparicio <jorge@japaric.io>
Date: Fri, 13 Jul 2018 19:38:51 -0500
Subject: [PATCH 06/16] v0.1.0

---
 library/compiler-builtins/libm/CHANGELOG.md | 12 ++++++++++++
 library/compiler-builtins/libm/Cargo.toml   | 10 ++++++++--
 library/compiler-builtins/libm/README.md    |  9 +++++++--
 3 files changed, 27 insertions(+), 4 deletions(-)
 create mode 100644 library/compiler-builtins/libm/CHANGELOG.md

diff --git a/library/compiler-builtins/libm/CHANGELOG.md b/library/compiler-builtins/libm/CHANGELOG.md
new file mode 100644
index 000000000000..c3e74a814338
--- /dev/null
+++ b/library/compiler-builtins/libm/CHANGELOG.md
@@ -0,0 +1,12 @@
+# Change Log
+
+All notable changes to this project will be documented in this file.
+This project adheres to [Semantic Versioning](http://semver.org/).
+
+## [Unreleased]
+
+## v0.1.0 - 2018-07-13
+
+- Initial release
+
+[Unreleased]: https://github.com/japaric/libm/compare/v0.1.0...HEAD
diff --git a/library/compiler-builtins/libm/Cargo.toml b/library/compiler-builtins/libm/Cargo.toml
index e3498eed0381..5a1ae4a6c92b 100644
--- a/library/compiler-builtins/libm/Cargo.toml
+++ b/library/compiler-builtins/libm/Cargo.toml
@@ -1,7 +1,13 @@
 [package]
-name = "libm"
-version = "0.1.0"
 authors = ["Jorge Aparicio <jorge@japaric.io>"]
+categories = ["no-std"]
+description = "libm in pure Rust"
+documentation = "https://docs.rs/libm"
+keywords = ["libm", "math"]
+license = "MIT OR Apache-2.0"
+name = "libm"
+repository = "https://github.com/japaric/libm"
+version = "0.1.0"
 
 [workspace]
 members = ["cb", "test-generator"]
\ No newline at end of file
diff --git a/library/compiler-builtins/libm/README.md b/library/compiler-builtins/libm/README.md
index ce731a203d60..6d8f9c49cc3c 100644
--- a/library/compiler-builtins/libm/README.md
+++ b/library/compiler-builtins/libm/README.md
@@ -6,8 +6,13 @@ A port of [MUSL]'s libm to Rust.
 
 ## Goals
 
-The short term goal of this library is to enable math support (e.g. `sin`, `atan2`) for the
-`wasm32-unknown-unknown` target. The longer term goal is to enable math support in the `core` crate.
+The short term goal of this library is to [enable math support (e.g. `sin`, `atan2`) for the
+`wasm32-unknown-unknown` target][wasm] (cf. [rust-lang-nursery/compiler-builtins][pr]). The longer
+term goal is to enable [math support in the `core` crate][core].
+
+[wasm]: https://github.com/japaric/libm/milestone/1
+[pr]: https://github.com/rust-lang-nursery/compiler-builtins/pull/248
+[core]: https://github.com/japaric/libm/milestone/2
 
 ## Contributing
 

From 9a9522cf4795a9aaf49458a914c964f98733a8b2 Mon Sep 17 00:00:00 2001
From: Jorge Aparicio <jorge@japaric.io>
Date: Fri, 13 Jul 2018 20:25:27 -0500
Subject: [PATCH 07/16] README: note that this crate is on crates.io and
 already usable

---
 library/compiler-builtins/libm/README.md | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/library/compiler-builtins/libm/README.md b/library/compiler-builtins/libm/README.md
index 6d8f9c49cc3c..02de9765a50b 100644
--- a/library/compiler-builtins/libm/README.md
+++ b/library/compiler-builtins/libm/README.md
@@ -14,6 +14,30 @@ term goal is to enable [math support in the `core` crate][core].
 [pr]: https://github.com/rust-lang-nursery/compiler-builtins/pull/248
 [core]: https://github.com/japaric/libm/milestone/2
 
+## Already usable
+
+This crate is [on crates.io] and can be used today in stable `#![no_std]` programs like this:
+
+[on crates.io]: https://crates.io/crates/libm
+
+``` rust
+#![no_std]
+
+extern crate libm;
+
+use libm::F32Ext; // adds methods to `f32`
+
+fn foo(x: f32) {
+    let y = x.sqrt();
+    let z = libm::truncf(x);
+}
+```
+
+Not all the math functions are available at the moment. Check the [API docs] to learn what's
+currently supported.
+
+[API docs]: https://docs.rs/libm
+
 ## Contributing
 
 Please check [CONTRIBUTING.md](CONTRIBUTING.md)

From bc94c70687c467d7fa4c655b90033de99d27211c Mon Sep 17 00:00:00 2001
From: Joseph Ryan <josephryan3.14@gmail.com>
Date: Fri, 13 Jul 2018 20:46:09 -0500
Subject: [PATCH 08/16] implement roundf

---
 library/compiler-builtins/libm/src/lib.rs     |  2 --
 .../compiler-builtins/libm/src/math/mod.rs    |  8 +++--
 .../compiler-builtins/libm/src/math/roundf.rs | 33 +++++++++++++++++++
 .../libm/test-generator/src/main.rs           |  2 +-
 4 files changed, 40 insertions(+), 5 deletions(-)
 create mode 100644 library/compiler-builtins/libm/src/math/roundf.rs

diff --git a/library/compiler-builtins/libm/src/lib.rs b/library/compiler-builtins/libm/src/lib.rs
index 0d13590c7ecc..b87e82b2ac6a 100644
--- a/library/compiler-builtins/libm/src/lib.rs
+++ b/library/compiler-builtins/libm/src/lib.rs
@@ -41,7 +41,6 @@ pub trait F32Ext {
     #[cfg(todo)]
     fn ceil(self) -> Self;
 
-    #[cfg(todo)]
     fn round(self) -> Self;
 
     #[cfg(todo)]
@@ -160,7 +159,6 @@ impl F32Ext for f32 {
         ceilf(self)
     }
 
-    #[cfg(todo)]
     #[inline]
     fn round(self) -> Self {
         roundf(self)
diff --git a/library/compiler-builtins/libm/src/math/mod.rs b/library/compiler-builtins/libm/src/math/mod.rs
index 41359bf8c059..8032bdabf9ac 100644
--- a/library/compiler-builtins/libm/src/math/mod.rs
+++ b/library/compiler-builtins/libm/src/math/mod.rs
@@ -1,7 +1,9 @@
 macro_rules! force_eval {
     ($e:expr) => {
-        unsafe { ::core::ptr::read_volatile(&$e); }
-    }
+        unsafe {
+            ::core::ptr::read_volatile(&$e);
+        }
+    };
 }
 
 mod fabs;
@@ -9,6 +11,7 @@ mod fabsf;
 mod fmodf;
 mod powf;
 mod round;
+mod roundf;
 mod scalbnf;
 mod sqrtf;
 
@@ -17,6 +20,7 @@ pub use self::fabsf::fabsf;
 pub use self::fmodf::fmodf;
 pub use self::powf::powf;
 pub use self::round::round;
+pub use self::roundf::roundf;
 pub use self::scalbnf::scalbnf;
 pub use self::sqrtf::sqrtf;
 
diff --git a/library/compiler-builtins/libm/src/math/roundf.rs b/library/compiler-builtins/libm/src/math/roundf.rs
new file mode 100644
index 000000000000..bd2488fa99c8
--- /dev/null
+++ b/library/compiler-builtins/libm/src/math/roundf.rs
@@ -0,0 +1,33 @@
+use core::f32;
+
+const TOINT: f32 = 1.0 / f32::EPSILON;
+
+pub fn roundf(mut x: f32) -> f32 {
+    let i = x.to_bits();
+    let e: u32 = i >> 23 & 0xff;
+    let mut y: f32;
+
+    if e >= 0x7f + 23 {
+        return x;
+    }
+    if i >> 31 != 0 {
+        x = -x;
+    }
+    if e < 0x7f - 1 {
+        force_eval!(x + TOINT);
+        return 0.0 * x;
+    }
+    y = x + TOINT - TOINT - x;
+    if y > 0.5f32 {
+        y = y + x - 1.0;
+    } else if y <= -0.5f32 {
+        y = y + x + 1.0;
+    } else {
+        y = y + x;
+    }
+    if i >> 31 != 0 {
+        -y
+    } else {
+        y
+    }
+}
diff --git a/library/compiler-builtins/libm/test-generator/src/main.rs b/library/compiler-builtins/libm/test-generator/src/main.rs
index 5ff78ffc8b37..2f78a8ed38da 100644
--- a/library/compiler-builtins/libm/test-generator/src/main.rs
+++ b/library/compiler-builtins/libm/test-generator/src/main.rs
@@ -574,7 +574,7 @@ f32_f32! {
     // fdimf,
     // log10f,
     // log2f,
-    // roundf,
+    roundf,
     // sinf,
     // sinhf,
     // tanf,

From 6237ba289068254c34fca5ad014a1cf8ba9ccbee Mon Sep 17 00:00:00 2001
From: Jack Mott <jack.mott@gmail.com>
Date: Fri, 13 Jul 2018 21:32:59 -0500
Subject: [PATCH 09/16] adding ceilf and floorf for issues rust-lang/libm#56
 and rust-lang/libm#54

---
 library/compiler-builtins/libm/src/lib.rs     |  4 ---
 .../compiler-builtins/libm/src/math/ceilf.rs  | 29 ++++++++++++++++++
 .../compiler-builtins/libm/src/math/floorf.rs | 30 +++++++++++++++++++
 .../compiler-builtins/libm/src/math/mod.rs    |  4 +++
 .../libm/test-generator/src/main.rs           |  4 +--
 5 files changed, 65 insertions(+), 6 deletions(-)
 create mode 100644 library/compiler-builtins/libm/src/math/ceilf.rs
 create mode 100644 library/compiler-builtins/libm/src/math/floorf.rs

diff --git a/library/compiler-builtins/libm/src/lib.rs b/library/compiler-builtins/libm/src/lib.rs
index 13e038bfc3be..783cc9e1818b 100644
--- a/library/compiler-builtins/libm/src/lib.rs
+++ b/library/compiler-builtins/libm/src/lib.rs
@@ -34,10 +34,8 @@ pub fn _eq(a: u64, b: u64) -> bool {
 ///
 /// This trait is sealed and cannot be implemented outside of `libm`.
 pub trait F32Ext: private::Sealed {
-    #[cfg(todo)]
     fn floor(self) -> Self;
 
-    #[cfg(todo)]
     fn ceil(self) -> Self;
 
     #[cfg(todo)]
@@ -142,13 +140,11 @@ pub trait F32Ext: private::Sealed {
 }
 
 impl F32Ext for f32 {
-    #[cfg(todo)]
     #[inline]
     fn floor(self) -> Self {
         floorf(self)
     }
 
-    #[cfg(todo)]
     #[inline]
     fn ceil(self) -> Self {
         ceilf(self)
diff --git a/library/compiler-builtins/libm/src/math/ceilf.rs b/library/compiler-builtins/libm/src/math/ceilf.rs
new file mode 100644
index 000000000000..b4f58bfb86f3
--- /dev/null
+++ b/library/compiler-builtins/libm/src/math/ceilf.rs
@@ -0,0 +1,29 @@
+use core::f32;
+
+pub fn ceilf(x: f32) -> f32 {
+    let mut ui = x.to_bits();
+    let e = (((ui >> 23) & 0xff) - 0x7f) as i32;
+
+    if e >= 23 {
+        return x;
+    }
+    if e >= 0 {
+        let m = 0x007fffff >> e;
+        if (ui & m) == 0 {
+            return x;
+        }
+        force_eval!(x + f32::from_bits(0x7b800000));
+        if ui >> 31 == 0 {
+            ui += m;
+        }
+        ui &= !m;
+    } else {
+        force_eval!(x + f32::from_bits(0x7b800000));
+        if ui >> 31 != 0 {
+            return -0.0;
+        } else if ui << 1 != 0 {
+            return 1.0;
+        }
+    }
+    return f32::from_bits(ui);
+}
diff --git a/library/compiler-builtins/libm/src/math/floorf.rs b/library/compiler-builtins/libm/src/math/floorf.rs
new file mode 100644
index 000000000000..9c263b51828b
--- /dev/null
+++ b/library/compiler-builtins/libm/src/math/floorf.rs
@@ -0,0 +1,30 @@
+use core::f32;
+
+#[inline]
+pub fn floorf(x: f32) -> f32 {
+    let mut ui = x.to_bits();
+    let e = (((ui >> 23) & 0xff) - 0x7f) as i32;
+
+    if e >= 23 {
+        return x;
+    }
+    if e >= 0 {
+        let m: u32 = 0x007fffff >> e;
+        if (ui & m) == 0 {
+            return x;
+        }
+        force_eval!(x + f32::from_bits(0x7b800000));
+        if ui >> 31 != 0 {
+            ui += m;
+        }
+        ui &= !m;
+    } else {
+        force_eval!(x + f32::from_bits(0x7b800000));
+        if ui >> 31 == 0 {
+            ui = 0;
+        } else if ui << 1 != 0 {
+            return -1.0;
+        }
+    }
+    return f32::from_bits(ui);
+}
diff --git a/library/compiler-builtins/libm/src/math/mod.rs b/library/compiler-builtins/libm/src/math/mod.rs
index 444652e81eff..2ddaa2728354 100644
--- a/library/compiler-builtins/libm/src/math/mod.rs
+++ b/library/compiler-builtins/libm/src/math/mod.rs
@@ -4,8 +4,10 @@ macro_rules! force_eval {
     }
 }
 
+mod ceilf;
 mod fabs;
 mod fabsf;
+mod floorf;
 mod fmodf;
 mod powf;
 mod round;
@@ -24,8 +26,10 @@ mod hypotf;
 //mod service;
 
 pub use self::{
+    ceilf::ceilf,
     fabs::fabs,
     fabsf::fabsf,
+    floorf::floorf,
     fmodf::fmodf,
     powf::powf,
     round::round,
diff --git a/library/compiler-builtins/libm/test-generator/src/main.rs b/library/compiler-builtins/libm/test-generator/src/main.rs
index ce20e80d1952..1d6168e4bc2a 100644
--- a/library/compiler-builtins/libm/test-generator/src/main.rs
+++ b/library/compiler-builtins/libm/test-generator/src/main.rs
@@ -652,12 +652,12 @@ fn main() -> Result<(), Box<Error>> {
 // With signature `fn(f32) -> f32`
 f32_f32! {
     // acosf,
-    // floorf,
+    floorf,
     truncf,
     // asinf,
     // atanf,
     // cbrtf,
-    // ceilf,
+    ceilf,
     // cosf,
     // coshf,
     // exp2f,

From 8bdbe460728b1de630b96a3164bb448b5083a007 Mon Sep 17 00:00:00 2001
From: Jorge Aparicio <jorge@japaric.io>
Date: Fri, 13 Jul 2018 21:51:07 -0500
Subject: [PATCH 10/16] run cargo-fmt

---
 .../compiler-builtins/libm/src/math/expf.rs   | 73 ++++++++++---------
 .../compiler-builtins/libm/src/math/floor.rs  | 32 ++++----
 .../compiler-builtins/libm/src/math/hypot.rs  | 14 ++--
 .../compiler-builtins/libm/src/math/hypotf.rs | 10 +--
 .../compiler-builtins/libm/src/math/logf.rs   | 45 ++++++------
 .../compiler-builtins/libm/src/math/mod.rs    | 32 ++------
 .../compiler-builtins/libm/src/math/round.rs  |  2 +-
 .../compiler-builtins/libm/src/math/scalbn.rs | 12 +--
 .../libm/src/math/scalbnf.rs                  | 12 +--
 .../compiler-builtins/libm/src/math/sqrt.rs   | 60 +++++++--------
 10 files changed, 143 insertions(+), 149 deletions(-)

diff --git a/library/compiler-builtins/libm/src/math/expf.rs b/library/compiler-builtins/libm/src/math/expf.rs
index 1b645654e369..cffb557719f0 100644
--- a/library/compiler-builtins/libm/src/math/expf.rs
+++ b/library/compiler-builtins/libm/src/math/expf.rs
@@ -1,60 +1,67 @@
 use super::scalbnf;
 
-const HALF    : [f32; 2] = [0.5,-0.5];
-const LN2_HI  : f32      = 6.9314575195e-01;  /* 0x3f317200 */
-const LN2_LO  : f32      = 1.4286067653e-06;  /* 0x35bfbe8e */
-const INV_LN2 : f32      = 1.4426950216e+00;  /* 0x3fb8aa3b */
+const HALF: [f32; 2] = [0.5, -0.5];
+const LN2_HI: f32 = 6.9314575195e-01; /* 0x3f317200 */
+const LN2_LO: f32 = 1.4286067653e-06; /* 0x35bfbe8e */
+const INV_LN2: f32 = 1.4426950216e+00; /* 0x3fb8aa3b */
 /*
  * Domain [-0.34568, 0.34568], range ~[-4.278e-9, 4.447e-9]:
  * |x*(exp(x)+1)/(exp(x)-1) - p(x)| < 2**-27.74
  */
-const P1 : f32 =  1.6666625440e-1;    /*  0xaaaa8f.0p-26 */
-const P2 : f32 = -2.7667332906e-3;    /* -0xb55215.0p-32 */
+const P1: f32 = 1.6666625440e-1; /*  0xaaaa8f.0p-26 */
+const P2: f32 = -2.7667332906e-3; /* -0xb55215.0p-32 */
 
 #[inline]
 pub fn expf(mut x: f32) -> f32 {
-    let x1p127  = f32::from_bits(0x7f000000); // 0x1p127f === 2 ^ 127
-    let x1p_126 = f32::from_bits(0x800000);   // 0x1p-126f === 2 ^ -126  /*original 0x1p-149f    ??????????? */
-    
+    let x1p127 = f32::from_bits(0x7f000000); // 0x1p127f === 2 ^ 127
+    let x1p_126 = f32::from_bits(0x800000); // 0x1p-126f === 2 ^ -126  /*original 0x1p-149f    ??????????? */
+
     let mut hx = x.to_bits();
-    let sign = (hx >> 31) as i32;   /* sign bit of x */
-    let signb : bool = sign != 0;
-    hx &= 0x7fffffff;  /* high word of |x| */
-    
+    let sign = (hx >> 31) as i32; /* sign bit of x */
+    let signb: bool = sign != 0;
+    hx &= 0x7fffffff; /* high word of |x| */
+
     /* special cases */
-    if hx >= 0x42aeac50 {   /* if |x| >= -87.33655f or NaN */
-        if hx > 0x7f800000 {/* NaN */
+    if hx >= 0x42aeac50 {
+        /* if |x| >= -87.33655f or NaN */
+        if hx > 0x7f800000 {
+            /* NaN */
             return x;
         }
-        if (hx >= 0x42b17218) && (!signb) {  /* x >= 88.722839f */
+        if (hx >= 0x42b17218) && (!signb) {
+            /* x >= 88.722839f */
             /* overflow */
             x *= x1p127;
             return x;
         }
         if signb {
             /* underflow */
-            force_eval!(-x1p_126/x);
-            if hx >= 0x42cff1b5 { /* x <= -103.972084f */
-                return 0.
+            force_eval!(-x1p_126 / x);
+            if hx >= 0x42cff1b5 {
+                /* x <= -103.972084f */
+                return 0.;
             }
         }
     }
-    
+
     /* argument reduction */
-    let k  : i32;
-    let hi : f32;
-    let lo : f32;
-    if hx > 0x3eb17218 {     /* if |x| > 0.5 ln2 */
-        if hx > 0x3f851592 { /* if |x| > 1.5 ln2 */
-            k = (INV_LN2*x + HALF[sign as usize]) as i32;
+    let k: i32;
+    let hi: f32;
+    let lo: f32;
+    if hx > 0x3eb17218 {
+        /* if |x| > 0.5 ln2 */
+        if hx > 0x3f851592 {
+            /* if |x| > 1.5 ln2 */
+            k = (INV_LN2 * x + HALF[sign as usize]) as i32;
         } else {
             k = 1 - sign - sign;
         }
         let kf = k as f32;
-        hi = x - kf*LN2_HI;  /* k*ln2hi is exact here */
-        lo = kf*LN2_LO;
+        hi = x - kf * LN2_HI; /* k*ln2hi is exact here */
+        lo = kf * LN2_LO;
         x = hi - lo;
-    } else if hx > 0x39000000 {  /* |x| > 2**-14 */
+    } else if hx > 0x39000000 {
+        /* |x| > 2**-14 */
         k = 0;
         hi = x;
         lo = 0.;
@@ -63,11 +70,11 @@ pub fn expf(mut x: f32) -> f32 {
         force_eval!(x1p127 + x);
         return 1. + x;
     }
-    
+
     /* x is now in primary range */
-    let xx = x*x;
-    let c = x - xx*(P1+xx*P2);
-    let y = 1. + (x*c/(2.-c) - lo + hi);
+    let xx = x * x;
+    let c = x - xx * (P1 + xx * P2);
+    let y = 1. + (x * c / (2. - c) - lo + hi);
     if k == 0 {
         y
     } else {
diff --git a/library/compiler-builtins/libm/src/math/floor.rs b/library/compiler-builtins/libm/src/math/floor.rs
index a5fb1757413b..997865d39e93 100644
--- a/library/compiler-builtins/libm/src/math/floor.rs
+++ b/library/compiler-builtins/libm/src/math/floor.rs
@@ -1,27 +1,27 @@
 use core::f64;
 
-const TOINT    : f64 = 1. / f64::EPSILON;
+const TOINT: f64 = 1. / f64::EPSILON;
 
 #[inline]
-pub fn floor(x : f64) -> f64 {
+pub fn floor(x: f64) -> f64 {
     let ui = x.to_bits();
-	let e = ((ui >> 52) & 0x7ff) as i32;
+    let e = ((ui >> 52) & 0x7ff) as i32;
 
-	if (e >= 0x3ff+52) || (x == 0.) {
-		return x;
+    if (e >= 0x3ff + 52) || (x == 0.) {
+        return x;
     }
-	/* y = int(x) - x, where int(x) is an integer neighbor of x */
-	let y = if (ui >> 63) != 0 {
-		x - TOINT + TOINT - x
-	} else {
-		x + TOINT - TOINT - x
+    /* y = int(x) - x, where int(x) is an integer neighbor of x */
+    let y = if (ui >> 63) != 0 {
+        x - TOINT + TOINT - x
+    } else {
+        x + TOINT - TOINT - x
     };
-	/* special case because of non-nearest rounding modes */
-	if e <= 0x3ff-1 {
-		force_eval!(y);
-		return if (ui >> 63) != 0 { -1. } else { 0. };
-	}
-	if y > 0. {
+    /* special case because of non-nearest rounding modes */
+    if e <= 0x3ff - 1 {
+        force_eval!(y);
+        return if (ui >> 63) != 0 { -1. } else { 0. };
+    }
+    if y > 0. {
         x + y - 1.
     } else {
         x + y
diff --git a/library/compiler-builtins/libm/src/math/hypot.rs b/library/compiler-builtins/libm/src/math/hypot.rs
index dcc17d914fb9..7ad1baf796c8 100644
--- a/library/compiler-builtins/libm/src/math/hypot.rs
+++ b/library/compiler-builtins/libm/src/math/hypot.rs
@@ -12,8 +12,8 @@ fn sq(x: f64) -> (f64, f64) {
     xc = x * SPLIT;
     xh = x - xc + xc;
     xl = x - xh;
-    let hi = x*x;
-    let lo = xh*xh - hi + 2.*xh*xl + xl*xl;
+    let hi = x * x;
+    let lo = xh * xh - hi + 2. * xh * xl + xl * xl;
     (hi, lo)
 }
 
@@ -39,8 +39,8 @@ pub fn hypot(mut x: f64, mut y: f64) -> f64 {
     }
 
     /* special cases */
-    ex = (uxi>>52) as i64;
-    ey = (uyi>>52) as i64;
+    ex = (uxi >> 52) as i64;
+    ey = (uyi >> 52) as i64;
     x = f64::from_bits(uxi);
     y = f64::from_bits(uyi);
     /* note: hypot(inf,nan) == inf */
@@ -59,16 +59,16 @@ pub fn hypot(mut x: f64, mut y: f64) -> f64 {
     /* precise sqrt argument in nearest rounding mode without overflow */
     /* xh*xh must not overflow and xl*xl must not underflow in sq */
     z = 1.;
-    if ex > 0x3ff+510 {
+    if ex > 0x3ff + 510 {
         z = x1p700;
         x *= x1p_700;
         y *= x1p_700;
-    } else if ey < 0x3ff-450 {
+    } else if ey < 0x3ff - 450 {
         z = x1p_700;
         x *= x1p700;
         y *= x1p700;
     }
     let (hx, lx) = sq(x);
     let (hy, ly) = sq(y);
-    return z*sqrt(ly+lx+hy+hx);
+    return z * sqrt(ly + lx + hy + hx);
 }
diff --git a/library/compiler-builtins/libm/src/math/hypotf.rs b/library/compiler-builtins/libm/src/math/hypotf.rs
index 146aab4e4464..d59710ada395 100644
--- a/library/compiler-builtins/libm/src/math/hypotf.rs
+++ b/library/compiler-builtins/libm/src/math/hypotf.rs
@@ -22,22 +22,22 @@ pub fn hypotf(mut x: f32, mut y: f32) -> f32 {
 
     x = f32::from_bits(uxi);
     y = f32::from_bits(uyi);
-    if uyi == 0xff<<23 {
+    if uyi == 0xff << 23 {
         return y;
     }
-    if uxi >= 0xff<<23 || uyi == 0 || uxi - uyi >= 25<<23 {
+    if uxi >= 0xff << 23 || uyi == 0 || uxi - uyi >= 25 << 23 {
         return x + y;
     }
 
     z = 1.;
-    if uxi >= (0x7f+60)<<23 {
+    if uxi >= (0x7f + 60) << 23 {
         z = x1p90;
         x *= x1p_90;
         y *= x1p_90;
-    } else if uyi < (0x7f-60)<<23 {
+    } else if uyi < (0x7f - 60) << 23 {
         z = x1p_90;
         x *= x1p90;
         y *= x1p90;
     }
-    z*sqrtf((x as f64 * x as f64 + y as f64 * y as f64) as f32)
+    z * sqrtf((x as f64 * x as f64 + y as f64 * y as f64) as f32)
 }
diff --git a/library/compiler-builtins/libm/src/math/logf.rs b/library/compiler-builtins/libm/src/math/logf.rs
index 76b4ede19514..78c5e94ad92a 100644
--- a/library/compiler-builtins/libm/src/math/logf.rs
+++ b/library/compiler-builtins/libm/src/math/logf.rs
@@ -1,24 +1,25 @@
-const LN2_HI : f32 = 6.9313812256e-01;  /* 0x3f317180 */
-const LN2_LO : f32 = 9.0580006145e-06; /* 0x3717f7d1 */
+const LN2_HI: f32 = 6.9313812256e-01; /* 0x3f317180 */
+const LN2_LO: f32 = 9.0580006145e-06; /* 0x3717f7d1 */
 /* |(log(1+s)-log(1-s))/s - Lg(s)| < 2**-34.24 (~[-4.95e-11, 4.97e-11]). */
-const LG1    : f32 = 0.66666662693;  /*  0xaaaaaa.0p-24*/
-const LG2    : f32 = 0.40000972152;  /*  0xccce13.0p-25 */
-const LG3    : f32 = 0.28498786688;  /*  0x91e9ee.0p-25 */
-const LG4    : f32 = 0.24279078841; /*  0xf89e26.0p-26 */
+const LG1: f32 = 0.66666662693; /*  0xaaaaaa.0p-24*/
+const LG2: f32 = 0.40000972152; /*  0xccce13.0p-25 */
+const LG3: f32 = 0.28498786688; /*  0x91e9ee.0p-25 */
+const LG4: f32 = 0.24279078841; /*  0xf89e26.0p-26 */
 
 #[inline]
 pub fn logf(mut x: f32) -> f32 {
     let x1p25 = f32::from_bits(0x4c000000); // 0x1p25f === 2 ^ 25
-    
+
     let mut ix = x.to_bits();
     let mut k = 0i32;
-    
-    if (ix < 0x00800000) || ((ix>>31) != 0) {  /* x < 2**-126  */
-        if ix<<1 == 0 {
-            return -1./(x*x);  /* log(+-0)=-inf */
+
+    if (ix < 0x00800000) || ((ix >> 31) != 0) {
+        /* x < 2**-126  */
+        if ix << 1 == 0 {
+            return -1. / (x * x); /* log(+-0)=-inf */
         }
-        if (ix>>31) != 0 {
-            return (x-x)/0.;   /* log(-#) = NaN */
+        if (ix >> 31) != 0 {
+            return (x - x) / 0.; /* log(-#) = NaN */
         }
         /* subnormal number, scale up x */
         k -= 25;
@@ -32,18 +33,18 @@ pub fn logf(mut x: f32) -> f32 {
 
     /* reduce x into [sqrt(2)/2, sqrt(2)] */
     ix += 0x3f800000 - 0x3f3504f3;
-    k += ((ix>>23) as i32) - 0x7f;
+    k += ((ix >> 23) as i32) - 0x7f;
     ix = (ix & 0x007fffff) + 0x3f3504f3;
-    x =  f32::from_bits(ix);
+    x = f32::from_bits(ix);
 
     let f = x - 1.;
-    let s = f/(2. + f);
-    let z = s*s;
-    let w = z*z;
-    let t1 = w*(LG2+w*LG4);
-    let t2 = z*(LG1+w*LG3);
+    let s = f / (2. + f);
+    let z = s * s;
+    let w = z * z;
+    let t1 = w * (LG2 + w * LG4);
+    let t2 = z * (LG1 + w * LG3);
     let r = t2 + t1;
-    let hfsq = 0.5*f*f;
+    let hfsq = 0.5 * f * f;
     let dk = k as f32;
-    s*(hfsq+r) + dk*LN2_LO - hfsq + f + dk*LN2_HI
+    s * (hfsq + r) + dk * LN2_LO - hfsq + f + dk * LN2_HI
 }
diff --git a/library/compiler-builtins/libm/src/math/mod.rs b/library/compiler-builtins/libm/src/math/mod.rs
index d0121048d96b..c43199f825c3 100644
--- a/library/compiler-builtins/libm/src/math/mod.rs
+++ b/library/compiler-builtins/libm/src/math/mod.rs
@@ -7,10 +7,15 @@ macro_rules! force_eval {
 }
 
 mod ceilf;
+mod expf;
 mod fabs;
 mod fabsf;
+mod floor;
 mod floorf;
 mod fmodf;
+mod hypot;
+mod hypotf;
+mod logf;
 mod powf;
 mod round;
 mod roundf;
@@ -18,36 +23,15 @@ mod scalbn;
 mod scalbnf;
 mod sqrt;
 mod sqrtf;
-mod logf;
-mod expf;
-mod floor;
 mod trunc;
 mod truncf;
-mod hypot;
-mod hypotf;
 
 //mod service;
 
 pub use self::{
-    ceilf::ceilf,
-    fabs::fabs,
-    fabsf::fabsf,
-    floorf::floorf,
-    fmodf::fmodf,
-    powf::powf,
-    round::round,
-    roundf::roundf,
-    scalbn::scalbn,
-    scalbnf::scalbnf,
-    sqrt::sqrt,
-    sqrtf::sqrtf,
-    logf::logf,
-    expf::expf,
-    floor::floor,
-    trunc::trunc,
-    truncf::truncf,
-    hypot::hypot,
-    hypotf::hypotf,
+    ceilf::ceilf, expf::expf, fabs::fabs, fabsf::fabsf, floor::floor, floorf::floorf, fmodf::fmodf,
+    hypot::hypot, hypotf::hypotf, logf::logf, powf::powf, round::round, roundf::roundf,
+    scalbn::scalbn, scalbnf::scalbnf, sqrt::sqrt, sqrtf::sqrtf, trunc::trunc, truncf::truncf,
 };
 
 fn isnanf(x: f32) -> bool {
diff --git a/library/compiler-builtins/libm/src/math/round.rs b/library/compiler-builtins/libm/src/math/round.rs
index 2a9f67c1d0fa..73d431c51839 100644
--- a/library/compiler-builtins/libm/src/math/round.rs
+++ b/library/compiler-builtins/libm/src/math/round.rs
@@ -26,7 +26,7 @@ pub fn round(mut x: f64) -> f64 {
     } else {
         y = y + x;
     }
-    
+
     if i >> 63 != 0 {
         -y
     } else {
diff --git a/library/compiler-builtins/libm/src/math/scalbn.rs b/library/compiler-builtins/libm/src/math/scalbn.rs
index 76e06f03ece2..ad81072ddc98 100644
--- a/library/compiler-builtins/libm/src/math/scalbn.rs
+++ b/library/compiler-builtins/libm/src/math/scalbn.rs
@@ -1,11 +1,11 @@
 #[inline]
-pub fn scalbn(x : f64, mut n: i32) -> f64 {
-    let x1p1023  = f64::from_bits(0x7fe0000000000000); // 0x1p1023 === 2 ^ 1023
-    let x1p53    = f64::from_bits(0x4340000000000000); // 0x1p53 === 2 ^ 53
+pub fn scalbn(x: f64, mut n: i32) -> f64 {
+    let x1p1023 = f64::from_bits(0x7fe0000000000000); // 0x1p1023 === 2 ^ 1023
+    let x1p53 = f64::from_bits(0x4340000000000000); // 0x1p53 === 2 ^ 53
     let x1p_1022 = f64::from_bits(0x0010000000000000); // 0x1p-1022 === 2 ^ (-1022)
-    
+
     let mut y = x;
-    
+
     if n > 1023 {
         y *= x1p1023;
         n -= 1023;
@@ -29,5 +29,5 @@ pub fn scalbn(x : f64, mut n: i32) -> f64 {
             }
         }
     }
-    y*f64::from_bits(((0x3ff+n) as u64)<<52)
+    y * f64::from_bits(((0x3ff + n) as u64) << 52)
 }
diff --git a/library/compiler-builtins/libm/src/math/scalbnf.rs b/library/compiler-builtins/libm/src/math/scalbnf.rs
index 31f93d323c5c..901497e5e51d 100644
--- a/library/compiler-builtins/libm/src/math/scalbnf.rs
+++ b/library/compiler-builtins/libm/src/math/scalbnf.rs
@@ -1,9 +1,9 @@
 #[inline]
-pub fn scalbnf(mut x: f32, mut n : i32) -> f32 {
-    let x1p127  = f32::from_bits(0x7f000000); // 0x1p127f === 2 ^ 127
-    let x1p_126 = f32::from_bits(0x800000);   // 0x1p-126f === 2 ^ -126
-    let x1p24   = f32::from_bits(0x4b800000); // 0x1p24f === 2 ^ 24
-    
+pub fn scalbnf(mut x: f32, mut n: i32) -> f32 {
+    let x1p127 = f32::from_bits(0x7f000000); // 0x1p127f === 2 ^ 127
+    let x1p_126 = f32::from_bits(0x800000); // 0x1p-126f === 2 ^ -126
+    let x1p24 = f32::from_bits(0x4b800000); // 0x1p24f === 2 ^ 24
+
     if n > 127 {
         x *= x1p127;
         n -= 127;
@@ -25,5 +25,5 @@ pub fn scalbnf(mut x: f32, mut n : i32) -> f32 {
             }
         }
     }
-    x * f32::from_bits(((0x7f+n) as u32)<<23)
+    x * f32::from_bits(((0x7f + n) as u32) << 23)
 }
diff --git a/library/compiler-builtins/libm/src/math/sqrt.rs b/library/compiler-builtins/libm/src/math/sqrt.rs
index 49fc58fff03c..17de5a2e0308 100644
--- a/library/compiler-builtins/libm/src/math/sqrt.rs
+++ b/library/compiler-builtins/libm/src/math/sqrt.rs
@@ -22,60 +22,62 @@ pub fn sqrt(x: f64) -> f64 {
     ix1 = x.to_bits() as u32;
 
     /* take care of Inf and NaN */
-    if (ix0&0x7ff00000) == 0x7ff00000 {
-        return x*x + x;  /* sqrt(NaN)=NaN, sqrt(+inf)=+inf, sqrt(-inf)=sNaN */
+    if (ix0 & 0x7ff00000) == 0x7ff00000 {
+        return x * x + x; /* sqrt(NaN)=NaN, sqrt(+inf)=+inf, sqrt(-inf)=sNaN */
     }
     /* take care of zero */
     if ix0 <= 0 {
-        if ((ix0&!(sign as i32))|ix1 as i32) == 0 {
-            return x;  /* sqrt(+-0) = +-0 */
+        if ((ix0 & !(sign as i32)) | ix1 as i32) == 0 {
+            return x; /* sqrt(+-0) = +-0 */
         }
         if ix0 < 0 {
-            return (x - x) / (x - x);  /* sqrt(-ve) = sNaN */
+            return (x - x) / (x - x); /* sqrt(-ve) = sNaN */
         }
     }
     /* normalize x */
-    m = ix0>>20;
-    if m == 0 {  /* subnormal x */
+    m = ix0 >> 20;
+    if m == 0 {
+        /* subnormal x */
         while ix0 == 0 {
             m -= 21;
-            ix0 |= (ix1>>11) as i32;
+            ix0 |= (ix1 >> 11) as i32;
             ix1 <<= 21;
         }
-        i=0;
-        while (ix0&0x00100000) == 0 {
+        i = 0;
+        while (ix0 & 0x00100000) == 0 {
             i += 1;
             ix0 <<= 1;
         }
         m -= i - 1;
-        ix0 |= (ix1>>(32-i)) as i32;
+        ix0 |= (ix1 >> (32 - i)) as i32;
         ix1 <<= i;
     }
-    m -= 1023;    /* unbias exponent */
-    ix0 = (ix0&0x000fffff)|0x00100000;
-    if (m & 1) == 1 {  /* odd m, double x to make it even */
-        ix0 += ix0 + ((ix1&sign)>>31) as i32;
+    m -= 1023; /* unbias exponent */
+    ix0 = (ix0 & 0x000fffff) | 0x00100000;
+    if (m & 1) == 1 {
+        /* odd m, double x to make it even */
+        ix0 += ix0 + ((ix1 & sign) >> 31) as i32;
         ix1 += ix1;
     }
-    m >>= 1;      /* m = [m/2] */
+    m >>= 1; /* m = [m/2] */
 
     /* generate sqrt(x) bit by bit */
-    ix0 += ix0 + ((ix1&sign)>>31) as i32;
+    ix0 += ix0 + ((ix1 & sign) >> 31) as i32;
     ix1 += ix1;
     q = 0; /* [q,q1] = sqrt(x) */
     q1 = 0;
     s0 = 0;
     s1 = 0;
-    r = 0x00200000;        /* r = moving bit from right to left */
+    r = 0x00200000; /* r = moving bit from right to left */
 
     while r != 0 {
         t = s0 + r as i32;
         if t <= ix0 {
-            s0   = t + r as i32;
+            s0 = t + r as i32;
             ix0 -= t;
-            q   += r as i32;
+            q += r as i32;
         }
-        ix0 += ix0 + ((ix1&sign)>>31) as i32;
+        ix0 += ix0 + ((ix1 & sign) >> 31) as i32;
         ix1 += ix1;
         r >>= 1;
     }
@@ -83,10 +85,10 @@ pub fn sqrt(x: f64) -> f64 {
     r = sign;
     while r != 0 {
         t1 = s1 + r;
-        t  = s0;
+        t = s0;
         if t < ix0 || (t == ix0 && t1 <= ix1) {
             s1 = t1 + r;
-            if (t1&sign) == sign && (s1&sign) == 0 {
+            if (t1 & sign) == sign && (s1 & sign) == 0 {
                 s0 += 1;
             }
             ix0 -= t;
@@ -96,19 +98,19 @@ pub fn sqrt(x: f64) -> f64 {
             ix1 -= t1;
             q1 += r;
         }
-        ix0 += ix0 + ((ix1&sign)>>31) as i32;
+        ix0 += ix0 + ((ix1 & sign) >> 31) as i32;
         ix1 += ix1;
         r >>= 1;
     }
 
     /* use floating add to find out rounding direction */
-    if (ix0 as u32|ix1) != 0 {
+    if (ix0 as u32 | ix1) != 0 {
         z = 1.0 - TINY; /* raise inexact flag */
         if z >= 1.0 {
             z = 1.0 + TINY;
             if q1 == 0xffffffff {
                 q1 = 0;
-                q+=1;
+                q += 1;
             } else if z > 1.0 {
                 if q1 == 0xfffffffe {
                     q += 1;
@@ -119,9 +121,9 @@ pub fn sqrt(x: f64) -> f64 {
             }
         }
     }
-    ix0 = (q>>1) + 0x3fe00000;
-    ix1 = q1>>1;
-    if (q&1) == 1 {
+    ix0 = (q >> 1) + 0x3fe00000;
+    ix1 = q1 >> 1;
+    if (q & 1) == 1 {
         ix1 |= sign;
     }
     ix0 += m << 20;

From 6e6642b48ca0e66625266e4b106eeec364297f9b Mon Sep 17 00:00:00 2001
From: Jorge Aparicio <jorge@japaric.io>
Date: Fri, 13 Jul 2018 21:53:01 -0500
Subject: [PATCH 11/16] force PR code to be formatted

---
 library/compiler-builtins/libm/.travis.yml   | 2 ++
 library/compiler-builtins/libm/ci/install.sh | 2 ++
 library/compiler-builtins/libm/ci/script.sh  | 6 ++----
 3 files changed, 6 insertions(+), 4 deletions(-)

diff --git a/library/compiler-builtins/libm/.travis.yml b/library/compiler-builtins/libm/.travis.yml
index 0c0832793474..ae03b6601973 100644
--- a/library/compiler-builtins/libm/.travis.yml
+++ b/library/compiler-builtins/libm/.travis.yml
@@ -22,6 +22,8 @@ install:
   - bash ci/install.sh
 
 script:
+  # code must be already formatted
+  - cargo fmt -- --check
   - bash ci/script.sh
 
 after_script: set +e
diff --git a/library/compiler-builtins/libm/ci/install.sh b/library/compiler-builtins/libm/ci/install.sh
index efdbb06c206e..68dd0f337ac1 100644
--- a/library/compiler-builtins/libm/ci/install.sh
+++ b/library/compiler-builtins/libm/ci/install.sh
@@ -5,6 +5,8 @@ main() {
         cargo install cross
     fi
 
+    rustup component add rustfmt-preview
+
     rustup target add x86_64-unknown-linux-musl
 
     if [ $TARGET != x86_64-unknown-linux-gnu ]; then
diff --git a/library/compiler-builtins/libm/ci/script.sh b/library/compiler-builtins/libm/ci/script.sh
index 3db6bfeb12d9..d29003052508 100644
--- a/library/compiler-builtins/libm/ci/script.sh
+++ b/library/compiler-builtins/libm/ci/script.sh
@@ -10,10 +10,8 @@ main() {
     # generate tests
     cargo run --package test-generator --target x86_64-unknown-linux-musl
 
-    if cargo fmt --version >/dev/null 2>&1; then
-        # nicer syntax error messages (if any)
-        cargo fmt
-    fi
+    # nicer syntax error messages (if any)
+    cargo fmt
 
     # run tests
     cross test --target $TARGET --release

From 131cc1ac449a64d81ca371ae183f3fa2eeec1cf8 Mon Sep 17 00:00:00 2001
From: Jorge Aparicio <jorge@japaric.io>
Date: Fri, 13 Jul 2018 22:10:08 -0500
Subject: [PATCH 12/16] run cargo fmt -- --check on beta

---
 library/compiler-builtins/libm/.travis.yml   | 4 ++--
 library/compiler-builtins/libm/ci/install.sh | 7 +++++--
 library/compiler-builtins/libm/ci/script.sh  | 5 +++++
 3 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/library/compiler-builtins/libm/.travis.yml b/library/compiler-builtins/libm/.travis.yml
index ae03b6601973..2bbb60fc64d1 100644
--- a/library/compiler-builtins/libm/.travis.yml
+++ b/library/compiler-builtins/libm/.travis.yml
@@ -15,6 +15,8 @@ matrix:
     - env: TARGET=powerpc64-unknown-linux-gnu
     - env: TARGET=powerpc64le-unknown-linux-gnu
     - env: TARGET=x86_64-unknown-linux-gnu
+    - env: TARGET=cargo-fmt
+      rust: beta
 
 before_install: set -e
 
@@ -22,8 +24,6 @@ install:
   - bash ci/install.sh
 
 script:
-  # code must be already formatted
-  - cargo fmt -- --check
   - bash ci/script.sh
 
 after_script: set +e
diff --git a/library/compiler-builtins/libm/ci/install.sh b/library/compiler-builtins/libm/ci/install.sh
index 68dd0f337ac1..4d9552d231bc 100644
--- a/library/compiler-builtins/libm/ci/install.sh
+++ b/library/compiler-builtins/libm/ci/install.sh
@@ -1,12 +1,15 @@
 set -euxo pipefail
 
 main() {
+    if [ $TARGET = cargo-fmt ]; then
+        rustup component add rustfmt-preview
+        return
+    fi
+
     if ! hash cross >/dev/null 2>&1; then
         cargo install cross
     fi
 
-    rustup component add rustfmt-preview
-
     rustup target add x86_64-unknown-linux-musl
 
     if [ $TARGET != x86_64-unknown-linux-gnu ]; then
diff --git a/library/compiler-builtins/libm/ci/script.sh b/library/compiler-builtins/libm/ci/script.sh
index d29003052508..a4f1b324d660 100644
--- a/library/compiler-builtins/libm/ci/script.sh
+++ b/library/compiler-builtins/libm/ci/script.sh
@@ -1,6 +1,11 @@
 set -euxo pipefail
 
 main() {
+    if [ $TARGET = cargo-fmt ]; then
+        cargo fmt -- --check
+        return
+    fi
+
     # quick check
     cargo check
 

From ea8d02ae0f0eee219144fe2aa96679e384b6d110 Mon Sep 17 00:00:00 2001
From: Jorge Aparicio <jorge@japaric.io>
Date: Fri, 13 Jul 2018 22:15:21 -0500
Subject: [PATCH 13/16] make cargo fmt in ci/script.sh optional

---
 library/compiler-builtins/libm/ci/script.sh | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/library/compiler-builtins/libm/ci/script.sh b/library/compiler-builtins/libm/ci/script.sh
index a4f1b324d660..f2a294b488f5 100644
--- a/library/compiler-builtins/libm/ci/script.sh
+++ b/library/compiler-builtins/libm/ci/script.sh
@@ -15,8 +15,10 @@ main() {
     # generate tests
     cargo run --package test-generator --target x86_64-unknown-linux-musl
 
-    # nicer syntax error messages (if any)
-    cargo fmt
+    if cargo fmt --version >/dev/null 2>&1; then
+        # nicer syntax error messages (if any)
+        cargo fmt
+    fi
 
     # run tests
     cross test --target $TARGET --release

From 30c31d32d337c69d1f7ce5142e3ec8dcfaa50d47 Mon Sep 17 00:00:00 2001
From: Erik <erikdesjardins@users.noreply.github.com>
Date: Fri, 13 Jul 2018 23:40:57 -0400
Subject: [PATCH 14/16] implement log2 and log2f

---
 library/compiler-builtins/libm/src/lib.rs     |  4 -
 .../compiler-builtins/libm/src/math/log2.rs   | 86 +++++++++++++++++++
 .../compiler-builtins/libm/src/math/log2f.rs  | 71 +++++++++++++++
 .../compiler-builtins/libm/src/math/mod.rs    |  7 +-
 .../libm/test-generator/src/main.rs           |  4 +-
 5 files changed, 164 insertions(+), 8 deletions(-)
 create mode 100644 library/compiler-builtins/libm/src/math/log2.rs
 create mode 100644 library/compiler-builtins/libm/src/math/log2f.rs

diff --git a/library/compiler-builtins/libm/src/lib.rs b/library/compiler-builtins/libm/src/lib.rs
index 571cf365c8c8..0194722af66c 100644
--- a/library/compiler-builtins/libm/src/lib.rs
+++ b/library/compiler-builtins/libm/src/lib.rs
@@ -75,7 +75,6 @@ pub trait F32Ext: private::Sealed {
 
     fn log(self, base: Self) -> Self;
 
-    #[cfg(todo)]
     fn log2(self) -> Self;
 
     #[cfg(todo)]
@@ -228,7 +227,6 @@ impl F32Ext for f32 {
         self.ln() / base.ln()
     }
 
-    #[cfg(todo)]
     #[inline]
     fn log2(self) -> Self {
         log2f(self)
@@ -399,7 +397,6 @@ pub trait F64Ext: private::Sealed {
     #[cfg(todo)]
     fn log(self, base: Self) -> Self;
 
-    #[cfg(todo)]
     fn log2(self) -> Self;
 
     #[cfg(todo)]
@@ -557,7 +554,6 @@ impl F64Ext for f64 {
         self.ln() / base.ln()
     }
 
-    #[cfg(todo)]
     #[inline]
     fn log2(self) -> Self {
         log2(self)
diff --git a/library/compiler-builtins/libm/src/math/log2.rs b/library/compiler-builtins/libm/src/math/log2.rs
new file mode 100644
index 000000000000..c0d3263e3b46
--- /dev/null
+++ b/library/compiler-builtins/libm/src/math/log2.rs
@@ -0,0 +1,86 @@
+use core::f64;
+
+const IVLN2HI: f64 = 1.44269504072144627571e+00; /* 0x3ff71547, 0x65200000 */
+const IVLN2LO: f64 = 1.67517131648865118353e-10; /* 0x3de705fc, 0x2eefa200 */
+const LG1: f64 = 6.666666666666735130e-01; /* 3FE55555 55555593 */
+const LG2: f64 = 3.999999999940941908e-01; /* 3FD99999 9997FA04 */
+const LG3: f64 = 2.857142874366239149e-01; /* 3FD24924 94229359 */
+const LG4: f64 = 2.222219843214978396e-01; /* 3FCC71C5 1D8E78AF */
+const LG5: f64 = 1.818357216161805012e-01; /* 3FC74664 96CB03DE */
+const LG6: f64 = 1.531383769920937332e-01; /* 3FC39A09 D078C69F */
+const LG7: f64 = 1.479819860511658591e-01; /* 3FC2F112 DF3E5244 */
+
+pub fn log2(mut x: f64) -> f64 {
+    let x1p54 = f64::from_bits(0x4350000000000000); // 0x1p54 === 2 ^ 54
+
+    let mut ui: u64 = x.to_bits();
+    let hfsq: f64;
+    let f: f64;
+    let s: f64;
+    let z: f64;
+    let r: f64;
+    let mut w: f64;
+    let t1: f64;
+    let t2: f64;
+    let y: f64;
+    let mut hi: f64;
+    let lo: f64;
+    let mut val_hi: f64;
+    let mut val_lo: f64;
+    let mut hx: u32;
+    let mut k: i32;
+
+    hx = (ui >> 32) as u32;
+    k = 0;
+    if hx < 0x00100000 || (hx >> 31) > 0 {
+        if ui << 1 == 0 {
+            return -1. / (x * x); /* log(+-0)=-inf */
+        }
+        if (hx >> 31) > 0 {
+            return (x - x) / 0.0; /* log(-#) = NaN */
+        }
+        /* subnormal number, scale x up */
+        k -= 54;
+        x *= x1p54;
+        ui = x.to_bits();
+        hx = (ui >> 32) as u32;
+    } else if hx >= 0x7ff00000 {
+        return x;
+    } else if hx == 0x3ff00000 && ui << 32 == 0 {
+        return 0.;
+    }
+
+    /* reduce x into [sqrt(2)/2, sqrt(2)] */
+    hx += 0x3ff00000 - 0x3fe6a09e;
+    k += (hx >> 20) as i32 - 0x3ff;
+    hx = (hx & 0x000fffff) + 0x3fe6a09e;
+    ui = (hx as u64) << 32 | (ui & 0xffffffff);
+    x = f64::from_bits(ui);
+
+    f = x - 1.0;
+    hfsq = 0.5 * f * f;
+    s = f / (2.0 + f);
+    z = s * s;
+    w = z * z;
+    t1 = w * (LG2 + w * (LG4 + w * LG6));
+    t2 = z * (LG1 + w * (LG3 + w * (LG5 + w * LG7)));
+    r = t2 + t1;
+
+    /* hi+lo = f - hfsq + s*(hfsq+R) ~ log(1+f) */
+    hi = f - hfsq;
+    ui = hi.to_bits();
+    ui &= (-1i64 as u64) << 32;
+    hi = f64::from_bits(ui);
+    lo = f - hi - hfsq + s * (hfsq + r);
+
+    val_hi = hi * IVLN2HI;
+    val_lo = (lo + hi) * IVLN2LO + lo * IVLN2HI;
+
+    /* spadd(val_hi, val_lo, y), except for not using double_t: */
+    y = k.into();
+    w = y + val_hi;
+    val_lo += (y - w) + val_hi;
+    val_hi = w;
+
+    return val_lo + val_hi;
+}
diff --git a/library/compiler-builtins/libm/src/math/log2f.rs b/library/compiler-builtins/libm/src/math/log2f.rs
new file mode 100644
index 000000000000..47a917bdb8d2
--- /dev/null
+++ b/library/compiler-builtins/libm/src/math/log2f.rs
@@ -0,0 +1,71 @@
+use core::f32;
+
+const IVLN2HI: f32 = 1.4428710938e+00; /* 0x3fb8b000 */
+const IVLN2LO: f32 = -1.7605285393e-04; /* 0xb9389ad4 */
+/* |(log(1+s)-log(1-s))/s - Lg(s)| < 2**-34.24 (~[-4.95e-11, 4.97e-11]). */
+const LG1: f32 = 0.66666662693; /* 0xaaaaaa.0p-24 */
+const LG2: f32 = 0.40000972152; /* 0xccce13.0p-25 */
+const LG3: f32 = 0.28498786688; /* 0x91e9ee.0p-25 */
+const LG4: f32 = 0.24279078841; /* 0xf89e26.0p-26 */
+
+pub fn log2f(mut x: f32) -> f32 {
+    let x1p25f = f32::from_bits(0x4c000000); // 0x1p25f === 2 ^ 25
+
+    let mut ui: u32 = x.to_bits();
+    let hfsq: f32;
+    let f: f32;
+    let s: f32;
+    let z: f32;
+    let r: f32;
+    let w: f32;
+    let t1: f32;
+    let t2: f32;
+    let mut hi: f32;
+    let lo: f32;
+    let mut ix: u32;
+    let mut k: i32;
+
+    ix = ui;
+    k = 0;
+    if ix < 0x00800000 || (ix >> 31) > 0 {
+        /* x < 2**-126  */
+        if ix << 1 == 0 {
+            return -1. / (x * x); /* log(+-0)=-inf */
+        }
+        if (ix >> 31) > 0 {
+            return (x - x) / 0.0; /* log(-#) = NaN */
+        }
+        /* subnormal number, scale up x */
+        k -= 25;
+        x *= x1p25f;
+        ui = x.to_bits();
+        ix = ui;
+    } else if ix >= 0x7f800000 {
+        return x;
+    } else if ix == 0x3f800000 {
+        return 0.;
+    }
+
+    /* reduce x into [sqrt(2)/2, sqrt(2)] */
+    ix += 0x3f800000 - 0x3f3504f3;
+    k += (ix >> 23) as i32 - 0x7f;
+    ix = (ix & 0x007fffff) + 0x3f3504f3;
+    ui = ix;
+    x = f32::from_bits(ui);
+
+    f = x - 1.0;
+    s = f / (2.0 + f);
+    z = s * s;
+    w = z * z;
+    t1 = w * (LG2 + w * LG4);
+    t2 = z * (LG1 + w * LG3);
+    r = t2 + t1;
+    hfsq = 0.5 * f * f;
+
+    hi = f - hfsq;
+    ui = hi.to_bits();
+    ui &= 0xfffff000;
+    hi = f32::from_bits(ui);
+    lo = f - hi - hfsq + s * (hfsq + r);
+    return (lo + hi) * IVLN2LO + lo * IVLN2HI + hi * IVLN2HI + k as f32;
+}
diff --git a/library/compiler-builtins/libm/src/math/mod.rs b/library/compiler-builtins/libm/src/math/mod.rs
index c43199f825c3..a82c1ba7e592 100644
--- a/library/compiler-builtins/libm/src/math/mod.rs
+++ b/library/compiler-builtins/libm/src/math/mod.rs
@@ -15,6 +15,8 @@ mod floorf;
 mod fmodf;
 mod hypot;
 mod hypotf;
+mod log2;
+mod log2f;
 mod logf;
 mod powf;
 mod round;
@@ -30,8 +32,9 @@ mod truncf;
 
 pub use self::{
     ceilf::ceilf, expf::expf, fabs::fabs, fabsf::fabsf, floor::floor, floorf::floorf, fmodf::fmodf,
-    hypot::hypot, hypotf::hypotf, logf::logf, powf::powf, round::round, roundf::roundf,
-    scalbn::scalbn, scalbnf::scalbnf, sqrt::sqrt, sqrtf::sqrtf, trunc::trunc, truncf::truncf,
+    hypot::hypot, hypotf::hypotf, log2::log2, log2f::log2f, logf::logf, powf::powf, round::round,
+    roundf::roundf, scalbn::scalbn, scalbnf::scalbnf, sqrt::sqrt, sqrtf::sqrtf, trunc::trunc,
+    truncf::truncf,
 };
 
 fn isnanf(x: f32) -> bool {
diff --git a/library/compiler-builtins/libm/test-generator/src/main.rs b/library/compiler-builtins/libm/test-generator/src/main.rs
index 257232ca694a..7ec2292c3498 100644
--- a/library/compiler-builtins/libm/test-generator/src/main.rs
+++ b/library/compiler-builtins/libm/test-generator/src/main.rs
@@ -664,7 +664,7 @@ f32_f32! {
     expf,
     // fdimf,
     // log10f,
-    // log2f,
+    log2f,
     logf,
     roundf,
     // sinf,
@@ -709,7 +709,7 @@ f64_f64! {
     // log,
     // log10,
     // log1p,
-    // log2,
+    log2,
     round,
     // sin,
     // sinh,

From 65368071063a2b4a7d117301d67b6f3b66c70d1a Mon Sep 17 00:00:00 2001
From: Erik <erikdesjardins@users.noreply.github.com>
Date: Sat, 14 Jul 2018 00:24:22 -0400
Subject: [PATCH 15/16] implement log10 and log10f

---
 library/compiler-builtins/libm/src/lib.rs     |  4 -
 .../compiler-builtins/libm/src/math/log10.rs  | 98 +++++++++++++++++++
 .../compiler-builtins/libm/src/math/log10f.rs | 76 ++++++++++++++
 .../compiler-builtins/libm/src/math/mod.rs    |  8 +-
 .../libm/test-generator/src/main.rs           |  4 +-
 5 files changed, 181 insertions(+), 9 deletions(-)
 create mode 100644 library/compiler-builtins/libm/src/math/log10.rs
 create mode 100644 library/compiler-builtins/libm/src/math/log10f.rs

diff --git a/library/compiler-builtins/libm/src/lib.rs b/library/compiler-builtins/libm/src/lib.rs
index 0194722af66c..3ed89f729507 100644
--- a/library/compiler-builtins/libm/src/lib.rs
+++ b/library/compiler-builtins/libm/src/lib.rs
@@ -77,7 +77,6 @@ pub trait F32Ext: private::Sealed {
 
     fn log2(self) -> Self;
 
-    #[cfg(todo)]
     fn log10(self) -> Self;
 
     #[cfg(todo)]
@@ -232,7 +231,6 @@ impl F32Ext for f32 {
         log2f(self)
     }
 
-    #[cfg(todo)]
     #[inline]
     fn log10(self) -> Self {
         log10f(self)
@@ -399,7 +397,6 @@ pub trait F64Ext: private::Sealed {
 
     fn log2(self) -> Self;
 
-    #[cfg(todo)]
     fn log10(self) -> Self;
 
     #[cfg(todo)]
@@ -559,7 +556,6 @@ impl F64Ext for f64 {
         log2(self)
     }
 
-    #[cfg(todo)]
     #[inline]
     fn log10(self) -> Self {
         log10(self)
diff --git a/library/compiler-builtins/libm/src/math/log10.rs b/library/compiler-builtins/libm/src/math/log10.rs
new file mode 100644
index 000000000000..137d8966f521
--- /dev/null
+++ b/library/compiler-builtins/libm/src/math/log10.rs
@@ -0,0 +1,98 @@
+use core::f64;
+
+const IVLN10HI: f64 = 4.34294481878168880939e-01; /* 0x3fdbcb7b, 0x15200000 */
+const IVLN10LO: f64 = 2.50829467116452752298e-11; /* 0x3dbb9438, 0xca9aadd5 */
+const LOG10_2HI: f64 = 3.01029995663611771306e-01; /* 0x3FD34413, 0x509F6000 */
+const LOG10_2LO: f64 = 3.69423907715893078616e-13; /* 0x3D59FEF3, 0x11F12B36 */
+const LG1: f64 = 6.666666666666735130e-01; /* 3FE55555 55555593 */
+const LG2: f64 = 3.999999999940941908e-01; /* 3FD99999 9997FA04 */
+const LG3: f64 = 2.857142874366239149e-01; /* 3FD24924 94229359 */
+const LG4: f64 = 2.222219843214978396e-01; /* 3FCC71C5 1D8E78AF */
+const LG5: f64 = 1.818357216161805012e-01; /* 3FC74664 96CB03DE */
+const LG6: f64 = 1.531383769920937332e-01; /* 3FC39A09 D078C69F */
+const LG7: f64 = 1.479819860511658591e-01; /* 3FC2F112 DF3E5244 */
+
+#[inline]
+pub fn log10(mut x: f64) -> f64 {
+    let x1p54 = f64::from_bits(0x4350000000000000); // 0x1p54 === 2 ^ 54
+
+    let mut ui: u64 = x.to_bits();
+    let hfsq: f64;
+    let f: f64;
+    let s: f64;
+    let z: f64;
+    let r: f64;
+    let mut w: f64;
+    let t1: f64;
+    let t2: f64;
+    let dk: f64;
+    let y: f64;
+    let mut hi: f64;
+    let lo: f64;
+    let mut val_hi: f64;
+    let mut val_lo: f64;
+    let mut hx: u32;
+    let mut k: i32;
+
+    hx = (ui >> 32) as u32;
+    k = 0;
+    if hx < 0x00100000 || (hx >> 31) > 0 {
+        if ui << 1 == 0 {
+            return -1. / (x * x); /* log(+-0)=-inf */
+        }
+        if (hx >> 31) > 0 {
+            return (x - x) / 0.0; /* log(-#) = NaN */
+        }
+        /* subnormal number, scale x up */
+        k -= 54;
+        x *= x1p54;
+        ui = x.to_bits();
+        hx = (ui >> 32) as u32;
+    } else if hx >= 0x7ff00000 {
+        return x;
+    } else if hx == 0x3ff00000 && ui << 32 == 0 {
+        return 0.;
+    }
+
+    /* reduce x into [sqrt(2)/2, sqrt(2)] */
+    hx += 0x3ff00000 - 0x3fe6a09e;
+    k += (hx >> 20) as i32 - 0x3ff;
+    hx = (hx & 0x000fffff) + 0x3fe6a09e;
+    ui = (hx as u64) << 32 | (ui & 0xffffffff);
+    x = f64::from_bits(ui);
+
+    f = x - 1.0;
+    hfsq = 0.5 * f * f;
+    s = f / (2.0 + f);
+    z = s * s;
+    w = z * z;
+    t1 = w * (LG2 + w * (LG4 + w * LG6));
+    t2 = z * (LG1 + w * (LG3 + w * (LG5 + w * LG7)));
+    r = t2 + t1;
+
+    /* See log2.c for details. */
+    /* hi+lo = f - hfsq + s*(hfsq+R) ~ log(1+f) */
+    hi = f - hfsq;
+    ui = hi.to_bits();
+    ui &= (-1i64 as u64) << 32;
+    hi = f64::from_bits(ui);
+    lo = f - hi - hfsq + s * (hfsq + r);
+
+    /* val_hi+val_lo ~ log10(1+f) + k*log10(2) */
+    val_hi = hi * IVLN10HI;
+    dk = k as f64;
+    y = dk * LOG10_2HI;
+    val_lo = dk * LOG10_2LO + (lo + hi) * IVLN10LO + lo * IVLN10HI;
+
+    /*
+     * Extra precision in for adding y is not strictly needed
+     * since there is no very large cancellation near x = sqrt(2) or
+     * x = 1/sqrt(2), but we do it anyway since it costs little on CPUs
+     * with some parallelism and it reduces the error for many args.
+     */
+    w = y + val_hi;
+    val_lo += (y - w) + val_hi;
+    val_hi = w;
+
+    return val_lo + val_hi;
+}
diff --git a/library/compiler-builtins/libm/src/math/log10f.rs b/library/compiler-builtins/libm/src/math/log10f.rs
new file mode 100644
index 000000000000..58db093441f3
--- /dev/null
+++ b/library/compiler-builtins/libm/src/math/log10f.rs
@@ -0,0 +1,76 @@
+use core::f32;
+
+const IVLN10HI: f32 = 4.3432617188e-01; /* 0x3ede6000 */
+const IVLN10LO: f32 = -3.1689971365e-05; /* 0xb804ead9 */
+const LOG10_2HI: f32 = 3.0102920532e-01; /* 0x3e9a2080 */
+const LOG10_2LO: f32 = 7.9034151668e-07; /* 0x355427db */
+/* |(log(1+s)-log(1-s))/s - Lg(s)| < 2**-34.24 (~[-4.95e-11, 4.97e-11]). */
+const LG1: f32 = 0.66666662693; /* 0xaaaaaa.0p-24 */
+const LG2: f32 = 0.40000972152; /* 0xccce13.0p-25 */
+const LG3: f32 = 0.28498786688; /* 0x91e9ee.0p-25 */
+const LG4: f32 = 0.24279078841; /* 0xf89e26.0p-26 */
+
+#[inline]
+pub fn log10f(mut x: f32) -> f32 {
+    let x1p25f = f32::from_bits(0x4c000000); // 0x1p25f === 2 ^ 25
+
+    let mut ui: u32 = x.to_bits();
+    let hfsq: f32;
+    let f: f32;
+    let s: f32;
+    let z: f32;
+    let r: f32;
+    let w: f32;
+    let t1: f32;
+    let t2: f32;
+    let dk: f32;
+    let mut hi: f32;
+    let lo: f32;
+    let mut ix: u32;
+    let mut k: i32;
+
+    ix = ui;
+    k = 0;
+    if ix < 0x00800000 || (ix >> 31) > 0 {
+        /* x < 2**-126  */
+        if ix << 1 == 0 {
+            return -1. / (x * x); /* log(+-0)=-inf */
+        }
+        if (ix >> 31) > 0 {
+            return (x - x) / 0.0; /* log(-#) = NaN */
+        }
+        /* subnormal number, scale up x */
+        k -= 25;
+        x *= x1p25f;
+        ui = x.to_bits();
+        ix = ui;
+    } else if ix >= 0x7f800000 {
+        return x;
+    } else if ix == 0x3f800000 {
+        return 0.;
+    }
+
+    /* reduce x into [sqrt(2)/2, sqrt(2)] */
+    ix += 0x3f800000 - 0x3f3504f3;
+    k += (ix >> 23) as i32 - 0x7f;
+    ix = (ix & 0x007fffff) + 0x3f3504f3;
+    ui = ix;
+    x = f32::from_bits(ui);
+
+    f = x - 1.0;
+    s = f / (2.0 + f);
+    z = s * s;
+    w = z * z;
+    t1 = w * (LG2 + w * LG4);
+    t2 = z * (LG1 + w * LG3);
+    r = t2 + t1;
+    hfsq = 0.5 * f * f;
+
+    hi = f - hfsq;
+    ui = hi.to_bits();
+    ui &= 0xfffff000;
+    hi = f32::from_bits(ui);
+    lo = f - hi - hfsq + s * (hfsq + r);
+    dk = k as f32;
+    return dk * LOG10_2LO + (lo + hi) * IVLN10LO + lo * IVLN10HI + hi * IVLN10HI + dk * LOG10_2HI;
+}
diff --git a/library/compiler-builtins/libm/src/math/mod.rs b/library/compiler-builtins/libm/src/math/mod.rs
index a82c1ba7e592..828eef859085 100644
--- a/library/compiler-builtins/libm/src/math/mod.rs
+++ b/library/compiler-builtins/libm/src/math/mod.rs
@@ -15,6 +15,8 @@ mod floorf;
 mod fmodf;
 mod hypot;
 mod hypotf;
+mod log10;
+mod log10f;
 mod log2;
 mod log2f;
 mod logf;
@@ -32,9 +34,9 @@ mod truncf;
 
 pub use self::{
     ceilf::ceilf, expf::expf, fabs::fabs, fabsf::fabsf, floor::floor, floorf::floorf, fmodf::fmodf,
-    hypot::hypot, hypotf::hypotf, log2::log2, log2f::log2f, logf::logf, powf::powf, round::round,
-    roundf::roundf, scalbn::scalbn, scalbnf::scalbnf, sqrt::sqrt, sqrtf::sqrtf, trunc::trunc,
-    truncf::truncf,
+    hypot::hypot, hypotf::hypotf, log10::log10, log10f::log10f, log2::log2, log2f::log2f,
+    logf::logf, powf::powf, round::round, roundf::roundf, scalbn::scalbn, scalbnf::scalbnf,
+    sqrt::sqrt, sqrtf::sqrtf, trunc::trunc, truncf::truncf,
 };
 
 fn isnanf(x: f32) -> bool {
diff --git a/library/compiler-builtins/libm/test-generator/src/main.rs b/library/compiler-builtins/libm/test-generator/src/main.rs
index 7ec2292c3498..799a354a90af 100644
--- a/library/compiler-builtins/libm/test-generator/src/main.rs
+++ b/library/compiler-builtins/libm/test-generator/src/main.rs
@@ -663,7 +663,7 @@ f32_f32! {
     // exp2f,
     expf,
     // fdimf,
-    // log10f,
+    log10f,
     log2f,
     logf,
     roundf,
@@ -707,7 +707,7 @@ f64_f64! {
     // expm1,
     floor,
     // log,
-    // log10,
+    log10,
     // log1p,
     log2,
     round,

From bcafb03f6cdb51d14978de6117180af99829c746 Mon Sep 17 00:00:00 2001
From: Jorge Aparicio <jorge@japaric.io>
Date: Fri, 13 Jul 2018 23:34:37 -0500
Subject: [PATCH 16/16] update CONTRIBUTING

---
 library/compiler-builtins/libm/CONTRIBUTING.md | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/library/compiler-builtins/libm/CONTRIBUTING.md b/library/compiler-builtins/libm/CONTRIBUTING.md
index 1f0a05a3f8d9..6f8e984f3004 100644
--- a/library/compiler-builtins/libm/CONTRIBUTING.md
+++ b/library/compiler-builtins/libm/CONTRIBUTING.md
@@ -10,7 +10,8 @@
   can't, no problem! Your PR will be fully tested automatically. Though you may still want to add
   and run some unit tests. See the bottom of [`src/math/truncf.rs`] for an example of such tests;
   you can run unit tests with the `cargo test --lib` command.
-- Send us a pull request!
+- Send us a pull request! Make sure to run `cargo fmt` on your code before sending the PR. Also
+  include "closes #42" in the PR description to close the corresponding issue.
 - :tada:
 
 [issue tracker]: https://github.com/japaric/libm/issues